omap: fix clocksource_32k to start from zero

omap: fix clocksource_32k to start from zero

When the 32k sync timer is used for sched_clock(), it should count
time from the kernel boot (clocksource init) instead of the last HW
reset. Otherwise printk.time values will jump suddenly during the boot:

	[    0.000000] calling  omap2_clk_arch_init+0x0/0x138 @ 1
	[    0.000000] initcall omap2_clk_arch_init+0x0/0x138 returned -22 after 0 usecs
	[    0.000000] initcall omap2_clk_arch_init+0x0/0x138 returned with error code -22
	[    0.000000] calling  omap_init_clocksource_32k+0x0/0x98 @ 1
	[  508.697937] initcall omap_init_clocksource_32k+0x0/0x98 returned 0 after 0 usecs
	[  508.697967] calling  omap_init_devices+0x0/0x38 @ 1
	[  508.698425] initcall omap_init_devices+0x0/0x38 returned 0 after 0 usecs

This will confuse tools such as scripts/bootgraph.pl.

Signed-off-by: Aaro Koskinen <aaro.koskinen@nokia.com>
Acked-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>