MdeModulePkg: Change the algorithm in SNP to use the first found BAR index.

MdeModulePkg: Change the algorithm in SNP to use the first found BAR index.

The driver binding start function in SNP.c goes through all the BARs and get
the last BAR index for use. Theoretically it should work with all valid BARs,
but we got reports some device did always use the first valid BAR, so we change
the logic in SNP to use the first found BAR index instead of the last one.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Ye Ting <ting.ye@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18455 6f19259b-4bc3-4df7-8a09-765794883524