uboot-imx

ARM: keystone2: Use common definition for clk_get_rate

Since all the clocks are defined common, and has the same logic to get
the frequencies, use a common definition for for clk_get_rate().

Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>