KVM: x86: Move EMULTYPE_ALLOW_RETRY_PF to x86_emulate_instruction()

KVM: x86: Move EMULTYPE_ALLOW_RETRY_PF to x86_emulate_instruction()

Move the sanity checks for EMULTYPE_ALLOW_RETRY_PF to the top of
x86_emulate_instruction().  In addition to deduplicating a small amount
of code, this makes the connection between EMULTYPE_ALLOW_RETRY_PF and
EMULTYPE_PF even more explicit, and will allow dropping retry_instruction()
entirely.

Reviewed-by: Yuan Yao <yuan.yao@intel.com>
Link: https://lore.kernel.org/r/20240831001538.336683-11-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>