spi/mpc52xx-psc-spi: check for valid PSC
spi/mpc52xx-psc-spi: check for valid PSC

This driver calls mpc52xx_set_psc_clkdiv() but doesn't check its return value
to see if the PSC is actually valid for SPI use. Add the check and a hint for
the user.

Signed-off-by: Wolfram Sang <3883f8aab0424a154a3bcb43ff874b819786efbe@pengutronix.de>
Signed-off-by: Grant Likely <9069e6f5a2b566e2674a0ba1e2bf39c12c195fad@secretlab.ca>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs