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

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.

Fixes: ca3bf5d47cec ("iommu/amd: Introduces ivrs_acpihid kernel parameter")
Cc: stable@vger.kernel.org
Signed-off-by: Ilia.Gavrilov <Ilia.Gavrilov@infotecs.ru>
Reviewed-by: Kim Phillips <kim.phillips@amd.com>
Link: https://lore.kernel.org/r/20230202082719.1513849-1-Ilia.Gavrilov@infotecs.ru
Signed-off-by: Joerg Roedel <jroedel@suse.de>