Change in coreboot[master]: src/intel/microcode: Add support for extended signature table

[Nico Huber (Code Review)]

Attention is currently required from: Furquan Shaikh, Rizwan Qureshi, Tim Wawrzynczak.
Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/54734 )

Change subject: src/intel/microcode: Add support for extended signature table
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Patch Set 8:

(1 comment)

File src/cpu/intel/microcode/microcode.c:

https://review.coreboot.org/c/coreboot/+/54734/comment/bf3c1dc0_09564013 
PS8, Line 139: 	size_t ext_tbl_len = ucode->total_size - size;
ssize_t could be useful here to avoid overflows.

Especially given that `total_size` can be 0 as the comment below suggests.