OvmfPkg: add and use industry standard macro PIIX4_PMBA_MASK

OvmfPkg: add and use industry standard macro PIIX4_PMBA_MASK

We already have the identical purpose (but different value) macro for
ICH9, namely ICH9_PMBASE_MASK in
"OvmfPkg/Include/IndustryStandard/Q35MchIch9.h".

Also, stop bit-negating signed integer constants.

Cc: Gabriel Somlo <somlo@cmu.edu>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Ref: https://bugzilla.redhat.com/show_bug.cgi?id=1333238
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Tested-by: Gabriel Somlo <somlo@cmu.edu>