ARM:i.MX: fix build error in clock-mx51-mx53.c

arch/arm/mach-mx5/clock-mx51-mx53.c: In function 'clk_get_freq_dt':
arch/arm/mach-mx5/clock-mx51-mx53.c:1643: error: implicit declaration of function 'for_each_compatible_node'
arch/arm/mach-mx5/clock-mx51-mx53.c:1643: error: expected ';' before '{' token

Signed-off-by: Jason Liu <jason.hui@linaro.org>