spi: spi_flash: Fix the arguments of stm_is_locked_sr()

stm_is_locked_sr() takes the status register (SR) value as the last
parameter, not the second.

Based on a patch from Brian Norris for the linux kernel:
http://git.infradead.org/linux-mtd.git/commit/a32d5b726ff8cf32bf491522b0ac8ae2545a063e



Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Reviewed-by: Jagan Teki <jteki@openedev.com>