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.

@@ -118,7 +118,7 @@ void __init omap16xx_map_io(void)
 /*
  * Common low-level hardware init for omap1.
  */
-void omap1_init_early(void)
+void __init omap1_init_early(void)
 {
 	omap_check_revision();