fix: add eMMC device type in platform device (#1956)

Enabled eMMC boot with OS loader payload.

Signed-off-by: Kevin Tsai <kevin.tsai@intel.com>

Platform/AlderlakeBoardPkg/Library/Stage1BBoardInitLib/Stage1BBoardInitLib.c

@@ -92,6 +92,18 @@ CONST PLT_DEVICE mPlatformDevices[] = {
     .Type = OsBootDeviceUfs,
     .Instance = 1
   },
+  {
+    .Dev = {
+      .PciDev = {
+        .PciFunctionNumber  = PCI_FUNCTION_NUMBER_PCH_SCS_EMMC,
+        .PciDeviceNumber    = PCI_DEVICE_NUMBER_PCH_SCS_EMMC,
+        .PciBusNumber       = DEFAULT_PCI_BUS_NUMBER_PCH,
+        .IsMmioDevice       = 0
+      }
+    },
+    .Type = OsBootDeviceEmmc,
+    .Instance = 0
+  },
   {
     .Dev = {
       .PciDev = {