x86/ucode: Drop ops->free_patch()

x86/ucode: Drop ops->free_patch()

With the newly cleaned up vendor logic, each struct microcode_patch is a
trivial object in memory with no dependent allocations.

This is unlikely to change moving forwards, and function pointers are
expensive in the days of retpoline.  Move the responsibility to xfree() back
to common code.  If the need does arise in the future, we can consider
reintroducing the hook.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>