ARM: footbridge: trim down old ISA rtc setup

This fixes a "start_kernel(): bug: interrupts were enabled early".

rtc_cmos now takes care of initializing the ISA RTC and reading the
current time and date from it; there's no need to repeat that here,
thereby causing interrupts to be enabled too early.

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