[MIPS] arch/mips/au1000/time.c cleanup

Mark au1xxx_timer_setup() __init, just because it is. Get rid of
unneeded extern's (note that (*do_gettimeoffset)() is already declared by
<asm/time.c>) and an unused variable. Kill some whitespace...

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>