x86/Kconfig: Drop vendor dependency for X86_UMIP

Some Centaur family 7 CPUs and Zhaoxin family 7 CPUs support the UMIP
feature too. The text size growth which UMIP adds is ~1K and distro
kernels enable it anyway so remove the vendor dependency.

 [ bp: Rewrite commit message. ]

Signed-off-by: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/1583733990-2587-1-git-send-email-TonyWWang-oc@zhaoxin.com