OvmfPkg/QemuFwCfgLib: remove mQemuFwCfgSupported + mQemuFwCfgDmaSupported

Remove global variables, store the state in PlatformInfoHob instead.
Probing for fw_cfg happens on first use, at library initialization
time the Hob might not be present yet.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>

OvmfPkg/Include/Library/PlatformInitLib.h

@@ -50,6 +50,10 @@ typedef struct {
   UINT32               S3AcpiReservedMemorySize;
 
   UINT64               FeatureControlValue;
+
+  BOOLEAN              QemuFwCfgChecked;
+  BOOLEAN              QemuFwCfgSupported;
+  BOOLEAN              QemuFwCfgDmaSupported;
 } EFI_HOB_PLATFORM_INFO;
 #pragma pack()