ARM: PXA: eseries: fix eseries_register_clks section mismatch warning

Fix:

WARNING: vmlinux.o(.text+0x1a820): Section mismatch in reference from the function eseries_register_clks() to the function .init.text:clkdev_add_table()
The function eseries_register_clks() references
the function __init clkdev_add_table().
This is often because eseries_register_clks lacks a __init
annotation or the annotation of clkdev_add_table is wrong.

by adding the __init annotation to eseries_register_clks() - this
function is only called from other __init-marked functions.  While
we're here, mark it static as it's only called from within eseries.c.

Acked-by: Eric Miao <eric.y.miao@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>