KVM: x86: Drop superfluous check on direct MMU vs. WRITE_PF_TO_SP flag

KVM: x86: Drop superfluous check on direct MMU vs. WRITE_PF_TO_SP flag

Remove reexecute_instruction()'s final check on the MMU being direct, as
EMULTYPE_WRITE_PF_TO_SP is only ever set if the MMU is indirect, i.e. is a
shadow MMU.  Prior to commit 93c05d3ef252 ("KVM: x86: improve
reexecute_instruction"), the flag simply didn't exist (and KVM actually
returned "true" unconditionally for both types of MMUs).  I.e. the
explicit check for a direct MMU is simply leftover artifact from old code.

Link: https://lore.kernel.org/r/20240203002343.383056-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>