Refactor the timer code into version 1 and version 2.

Essentially there are 2 versions of the timer hardware on Freescale MXC
hardware. Version 1 is found on MX1/MXL, MX21 and MX27. Version 2 is found on
MX25, MX31, MX35, MX37, MX51, and future parts.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Amit Kucheria <amit.kucheria@canonical.com>