[OpenThread] ReceivePacket should use PBUF_LINK when allocating pbuf

[erjiaqing]

Problem

Currently, GenericThreadStackManagerImpl_OpenThread_LwIP::ReceivePacket uses pbuf_alloc(PBUF_RAW) to allocate pbuf for lwip, however, according to lwip's doc, PBUF_RAW should be used for allocating L2 packets, but infact, this function reads L3 packets, which should use PBUF_LINK to avoid potential issues.

Summary of Changes

Change PBUF_RAW to PBUF_LINK

[bukepo]

LGTM:+1:

[github-actions]

Size increase report for "gn_nrf-example-build"

File	Section	File	VM

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

[github-actions]

Size increase report for "gn_linux-example-build"

File	Section	File	VM

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

[github-actions]

Size increase report for "nrf-example-build"

File	Section	File	VM

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-nrf52840-lock-example.out and ./pull_artifact/chip-nrf52840-lock-example.out:

sections,vmsize,filesize

[github-actions]

Size increase report for "linux-example-build"

File	Section	File	VM

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-standalone-demo.out and ./pull_artifact/chip-standalone-demo.out:

sections,vmsize,filesize

[github-actions]

Size increase report for "esp32-example-build"

File	Section	File	VM

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-wifi-echo.elf and ./pull_artifact/chip-wifi-echo.elf:

sections,vmsize,filesize

[turon]

LGTM 👍