[ARM] tegra: Add timer support

v2: fixes from Russell King:
	- include linux/io.h instead of asm/io.h
    fixes from Gary King:
	- remove extra (and incorrect) irq definitions
	- use timer 3 instead of timer 1 for compatibility with other drivers
	- fix typo that disabled oneshot mode
v3:
	- Implement sched_clock
	- Fix checkpatch issues
    fixes from Gary King:
    	- Fix incorrect cycles calculation
	- Fix min_delta_ns assignment
    fixes from Linus Walleij:
	- use calc_mult_shift() instead of hard coding values

Signed-off-by: Colin Cross <ccross@android.com>