ARM: OMAP1: Fix section mismatch for omap1_init_early()

Fix the following warning:

WARNING: vmlinux.o(.text+0x1286c): Section mismatch in reference
from the function omap1_init_early() to the function .init.text:omap1_clk_init()
The function omap1_init_early() references
the function __init omap1_clk_init().
This is often because omap1_init_early lacks a __init 
annotation or the annotation of omap1_clk_init is wrong.

Signed-off-by: Tony Lindgren <tony@atomide.com>