ARM: OMAP1: Add checks for possible error condition in timer_init

On OMAP1, omap_32k_timer_init() function always returns "true",
irrespective of whether error occurred while initializing 32k sync
counter as a kernel clocksource or not and execution will never
fallback to mpu_timer clocksource init code.

This patch adds check for return value from function
omap_init_clocksource_32k(), and fallback to omap_mpu_timer_init()
in case of failure/error from omap_init_clocksource_32k().

Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
Acked-by: Kevin Hilman <khilman@ti.com>
Tested-by: Kevin Hilman <khilman@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>