[POWERPC] QE: change qe_setbrg() to take an enum qe_clock instead of an integer

qe_setbrg() currently takes an integer to indicate the BRG number.  Change that
to take an enum qe_clock instead, since this enum is intended to represent
clock sources.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>