ARC: Setup Vector Table Base in early boot

Otherwise early boot exceptions such as instructions errors due to
configuration mismatch between kernel and hardware go off to la-la land,
as opposed to hitting the handler and panic()'ing properly.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

diff --cc arch/arc/kernel/head.S
Simple merge

diff --cc arch/arc/kernel/irq.c
Simple merge