Pin code is used in the endian mode of the processor

[pjzander-signify]

Problem

The 32 bits pin code is passed to the function pbkdf2_sha256 as an array of 4 bytes. This is done by passing the address of the 32 bits pin code. However, this will fail on a big endian processor.

Proposed Solution

Convert the pin code to little endian format before passing to pbkdf2_sha256.