OvmfPkg/MemEncryptSevLib: skip page state change for Mmio address

OvmfPkg/MemEncryptSevLib: skip page state change for Mmio address

The SetMemoryEncDec() is used by the higher level routines to set or clear
the page encryption mask for system RAM and Mmio address. When SEV-SNP is
active, in addition to set/clear page mask it also updates the RMP table.
The RMP table updates are required for the system RAM address and not
the Mmio address.

Add a new parameter in SetMemoryEncDec() to tell whether the specified
address is Mmio. If its Mmio then skip the page state change in the RMP
table.

Cc: Michael Roth <michael.roth@amd.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Jiewen Yao <Jiewen.yao@intel.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>