video: fbdev: pxa168fb: Use devm_clk_get

This patch introduces the use of managed resource function
devm_clk_get instead of clk_get and removes corresponding calls
to clk_put in the probe and remove functions.

To be compatible with the change various gotos are replaced with
direct returns, and unneeded label failed_put_clk is dropped.

Signed-off-by: Vaishali Thakkar <vthakkar1994@gmail.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>