In lk 3.7.0-rc4 when a peripheral clock is not found for
a serial port the atmel_serial driver brings down the
kernel with an oops during boot-up. This impacts the
Atmel AT91 family of MCUs.

For example, arch/arm/mach-at91/at91sam9x5.c does not
specify properly the peripheral clocks for the UTXD0/URXD0
and UTXD1/URXD1 serial ports. Selecting either of those
ports in a dts file will crash the kernel. at91sam9x5.c needs
to be fixed but stopping atmel_serial crashing the kernel is
more urgent.

Patch attached for your consideration.

Signed-of-by: Douglas Gilbert <dgilbert@interlog.com>