ARM: mmp: fix timer_init calls

The change to passing the timer frequency as a function argument
was a good idea, but caused a build failure for one user that
was missed in the update:

arch/arm/mach-mmp/time.c: In function 'mmp_dt_init_timer':
arch/arm/mach-mmp/time.c:242:2: error: implicit declaration of function 'timer_init'; did you mean 'hrtimer_init'? [-Werror=implicit-function-declaration]

Change that as well to fix the build error, and rename the
function to put it into a proper namespace and make it clearer
what is actually going on.

I saw that the high 6500000 HZ frequency was previously only
set with CONFIG_MMP2, but is now also used with MMP (pxa910),
so I'm changing that back here. Please make sure that the
frequencies are all correct now.

Fixes: f36797ee ("ARM: mmp/mmp2: dt: enable the clock")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Olof Johansson <olof@lixom.net>