iommu/amd: Add a length limitation for the ivrs_acpihid command-line parameter

In the Linux kernel, the following vulnerability has been resolved:

iommu/amd: Add a length limitation for the ivrs_acpihid command-line parameter

The 'acpiid' buffer in the parse_ivrs_acpihid function may overflow,

because the string specifier in the format string sscanf()

has no width limitation.

Found by InfoTeCS on behalf of Linux Verification Center

(linuxtesting.org) with SVACE.