staging: mt7621-mmc: Fix style of braces

Fix checkpatch errors, warnings, checks about braces:
BRACES, ELSE_AFTER_BRACE, OPEN_BRACE

Signed-off-by: Christian Lütke-Stetzkamp <christian@lkamp.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>