ArmPkg/BdsLib: Close file after reading an Image

ArmPkg/BdsLib: Close file after reading an Image

When loading an image from a file, close the file after reading from it.
Use OpenProtocol instead of HandleProtocol to retrieve the simple file
system protocol interface.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ronald Cron <Ronald.Cron@arm.com>
Reviewed-by: Olivier Martin <olivier.martin@arm.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16586 6f19259b-4bc3-4df7-8a09-765794883524