ARM: 6359/1: ep93xx: move clock initialization earlier

Commit 7cfe2494

 ("ARM: AMBA: Add pclk support to AMBA bus
infrastructure") changed AMBA bus to handle the PCLK automatically.
However, in EP93xx clock initialization is arch_initcall which is done
later than AMBA device identification. This causes
amba_get_enable_pclk() to fail resulting device where UARTs are not
functional.

So change ep93xx_clock_init() to be postcore_initcall.

Signed-off-by: Mika Westerberg <mika.westerberg@iki.fi>
Acked-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>