[ARM] omap: allow double-registering of clocks

This stops things blowing up if a 'struct clk' to be passed more
than once to clk_register(), which will be required when we decouple
struct clk's from their names.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --cc arch/arm/plat-omap/clock.c
Simple merge