clk: imx6q: fix section mismatch warning

The imx6q_obtain_fixed_clk_hw lacks an __init marker, which
leads to this otherwise harmless warning:

WARNING: vmlinux.o(.text+0x495358): Section mismatch in reference from the function imx6q_obtain_fixed_clk_hw() to the function .init.text:imx_obtain_fixed_clock_hw()
The function imx6q_obtain_fixed_clk_hw() references
the function __init imx_obtain_fixed_clock_hw().
This is often because imx6q_obtain_fixed_clk_hw lacks a __init
annotation or the annotation of imx_obtain_fixed_clock_hw is wrong.

Fixes: 992b703b

 ("clk: imx6q: Switch to clk_hw based API")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>