magic number used for otp size for XS3

[xross]

lib_otpinfo/lib_otpinfo/src/otp_board_info.xc

Line 31 in ff95859

int address = 0x1fa;

This should use OTP_SIZE from otp3.h

It needs a /2 due to differential mode - we should add a comment about this.

I think we should also add a comment about the unit (words) - the define should ideally be OTP_SIZE_WORDS...