[ESP32] fix factory partition tool to only generate discriminator as well

[shubhamdp]

Problem

• scripts/tools/generate_esp32_chip_factory_bin.py throws exception when provided with only discriminator

Change overview

• Should be able to build an NVS binary image for quick tests with different discriminator

Tests

• Flashed the generated binary into nvs and commissioned different discriminator

[github-actions]

PR #25567: Size comparison from 536a0d9 to fb5b12b

Increases (1 build for cc32xx)

platform	target	config	section	536a0d9	fb5b12b	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL	.debug_info	20267387	20267388	1	0.0

Full report (1 build for cc32xx)

platform	target	config	section	536a0d9	fb5b12b	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	644425	644425	0	0.0
			(read/write)	203688	203688	0	0.0
			.ARM.attributes	44	44	0	0.0
			.ARM.exidx	8	8	0	0.0
			.bss	197088	197088	0	0.0
			.comment	194	194	0	0.0
			.data	1480	1480	0	0.0
			.debug_abbrev	930235	930235	0	0.0
			.debug_aranges	87344	87344	0	0.0
			.debug_frame	300044	300044	0	0.0
			.debug_info	20267387	20267388	1	0.0
			.debug_line	2659771	2659771	0	0.0
			.debug_loc	2802807	2802807	0	0.0
			.debug_ranges	282960	282960	0	0.0
			.debug_str	3024017	3024017	0	0.0
			.ramVecs	780	780	0	0.0
			.resetVecs	64	64	0	0.0
			.rodata	105929	105929	0	0.0
			.shstrtab	232	232	0	0.0
			.stab	204	204	0	0.0
			.stabstr	441	441	0	0.0
			.stack	2048	2048	0	0.0
			.strtab	378514	378514	0	0.0
			.symtab	256624	256624	0	0.0
			.text	536372	536372	0	0.0

[github-actions]

PR #25567: Size comparison from e497959 to b98a662

Decreases (1 build for cc32xx)

platform	target	config	section	e497959	b98a662	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL	.debug_info	20267388	20267386	-2	-0.0

Full report (1 build for cc32xx)

platform	target	config	section	e497959	b98a662	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	644425	644425	0	0.0
			(read/write)	203688	203688	0	0.0
			.ARM.attributes	44	44	0	0.0
			.ARM.exidx	8	8	0	0.0
			.bss	197088	197088	0	0.0
			.comment	194	194	0	0.0
			.data	1480	1480	0	0.0
			.debug_abbrev	930235	930235	0	0.0
			.debug_aranges	87344	87344	0	0.0
			.debug_frame	300044	300044	0	0.0
			.debug_info	20267388	20267386	-2	-0.0
			.debug_line	2659771	2659771	0	0.0
			.debug_loc	2802807	2802807	0	0.0
			.debug_ranges	282960	282960	0	0.0
			.debug_str	3024017	3024017	0	0.0
			.ramVecs	780	780	0	0.0
			.resetVecs	64	64	0	0.0
			.rodata	105929	105929	0	0.0
			.shstrtab	232	232	0	0.0
			.stab	204	204	0	0.0
			.stabstr	441	441	0	0.0
			.stack	2048	2048	0	0.0
			.strtab	378514	378514	0	0.0
			.symtab	256624	256624	0	0.0
			.text	536372	536372	0	0.0