staging/rts_pstor: fix single statements block warning

The following warning is fixed up.
drivers/staging/rts_pstor/sd.c:190: WARNING: braces {} are not necessary for single statement blocks

Signed-off-by: Devendra Naga <devendra.aaru@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>