staging/rts_pstor: fix the no brace needed warning

for if else statements having single block no braces are needed
fixed the following checkpatch warning

drivers/staging/rts_pstor/sd.c:140: WARNING: braces {} are not necessary for any arm of this statement

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