imx: timer: update gpt driver for i.MX6ULL

The i.MX6ULL's GPT supportting taking OSC as clock source.
Add i.MX6ULL support.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Ye Li <ye.li@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
Reviewed-by: Stefano Babic <sbabic@denx.de>
1 file changed