[ARM] i.MX: remove set_imx_fb_info() export

Remove not needed export and fix warning:

WARNING: vmlinux.o(__ksymtab+0x400): Section mismatch in reference from the variable __ksymtab_set_imx_fb_info to the function .init.text:set_imx_fb_info()
The symbol set_imx_fb_info is exported and annotated __init
Fix this by removing the __init annotation of set_imx_fb_info or drop the export.

Signed-off-by: Paulius Zaleckas <paulius.zaleckas@teltonika.lt>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>