clk: ti: fix dual-registration of uart4_ick

clk: ti: fix dual-registration of uart4_ick

On the OMAP AM3517 platform the uart4_ick gets registered
twice, causing any power management to /dev/ttyO3 to fail
when trying to wake the device up.

This solves the following oops:

[] Unhandled fault: external abort on non-linefetch (0x1028) at 0xfa09e008
[] PC is at serial_omap_pm+0x48/0x15c
[] LR is at _raw_spin_unlock_irqrestore+0x30/0x5c

Fixes: aafd900cab87 ("CLK: TI: add omap3 clock init file")
Cc: stable@vger.kernel.org
Cc: mturquette@baylibre.com
Cc: sboyd@codeaurora.org
Cc: linux-clk@vger.kernel.org
Cc: linux-omap@vger.kernel.org
Cc: linux-kernel@lists.codethink.co.uk
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Tero Kristo <t-kristo@ti.com>