avr32: Use the same entry point for reset and exception handling

avr32: Use the same entry point for reset and exception handling

Since the reset vector is always aligned to a very large boundary, we
can save a couple of KB worth of alignment padding by placing the
exception vectors at the same address.

Deciding which one it is is easy: If we're handling an exception, the
CPU is in Exception mode. If we're starting up after reset, the CPU is
in Supervisor mode. So this adds a very minimal overhead to the reset
path (only executed once) and the exception handling path (normally
never executed at all.)

Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>