KVM: x86: MMU: Consolidate quickly_check_mmio_pf() and is_mmio_page_fault()

These two have only slight differences:
 - whether 'addr' is of type u64 or of type gva_t
 - whether they have 'direct' parameter or not

Concerning the former, quickly_check_mmio_pf()'s u64 is better because
'addr' needs to be able to have both a guest physical address and a
guest virtual address.

The latter is just a stylistic issue as we can always calculate the mode
from the 'vcpu' as is_mmio_page_fault() does.  This patch keeps the
parameter to make the following patch cleaner.

In addition, the patch renames the function to mmio_info_in_cache() to
make it clear what it actually checks for.

Signed-off-by: Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>