OvmfPkg/BaseMemEncryptSevLib: clean up debug logging of PhysicalAddress

OvmfPkg/BaseMemEncryptSevLib: clean up debug logging of PhysicalAddress

In the SetMemoryEncDec() function, the way we currently report
PhysicalAddress is not uniform:

- mostly we say "for %lx",

- in one spot we say "at %lx" (even though the 2MB page being split does
  not live *at* PhysicalAddress, instead it maps PhysicalAddress),

- in another spot we don't log PhysicalAddress at all (when splitting a
  1GB page).

Unify this, using the format string "for Physical=0x%Lx".

Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>
Tested-by: Brijesh Singh <brijesh.singh@amd.com>