OvmfPkg/BaseMemEncryptSevLib: remove Flush parameter

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275

The Flush parameter is used to provide a hint whether the specified range
is Mmio address. Now that we have a dedicated helper to clear the
memory encryption mask for the Mmio address range, its safe to remove the
Flush parameter from MemEncryptSev{Set,Clear}PageEncMask().

Since the address specified in the MemEncryptSev{Set,Clear}PageEncMask()
points to a system RAM, thus a cache flush is required during the
encryption mask update.

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: Laszlo Ersek <lersek@redhat.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Message-Id: <20210519181949.6574-14-brijesh.singh@amd.com>

OvmfPkg/PlatformPei/AmdSev.c

@@ -72,8 +72,7 @@ AmdSevEsInitialize (
     DecryptStatus = MemEncryptSevClearPageEncMask (
       0,
       GhcbBasePa + EFI_PAGES_TO_SIZE (PageCount),
-      1,
-      TRUE
+      1
       );
     ASSERT_RETURN_ERROR (DecryptStatus);
   }