ARM: OMAP2+: gpmc: remove cs# in sync clk div calc

Divider value for a certain sync clk is determined solely
based on gpmc fclk. CS# does not have any role here, thus
remove presence of CS# in clock divider calculation API.

Signed-off-by: Afzal Mohammed <afzal@ti.com>
Reviewed-by: Jon Hunter <jon-hunter@ti.com>