staging: mt7621-spi: Remove unnecessary braces {} from single statement if block.

The patch fixes following checkpatch.pl issue:
WARNING : braces {} are not necessary for single statement blocks

Signed-off-by: Sankalp Negi <sankalpnegi2310@gmail.com>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>