EmbeddedPkg/MmcDxe: Create a periodic function to check if a card is present

In the former version, the check was done for every BlockIo operation.
By using a periodical function, we check less time in consequence performance
are better.



git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@12128 6f19259b-4bc3-4df7-8a09-765794883524

EmbeddedPkg/Universal/MmcDxe/Mmc.h

@@ -146,6 +146,8 @@ typedef struct _MMC_HOST_INSTANCE {
   EFI_BLOCK_IO_PROTOCOL     BlockIo;
   CARD_INFO                 CardInfo;
   EFI_MMC_HOST_PROTOCOL     *MmcHost;
+  
+  BOOLEAN                   Initialized;
 } MMC_HOST_INSTANCE;
 
 #define MMC_HOST_INSTANCE_SIGNATURE                 SIGNATURE_32('m', 'm', 'c', 'h')