[PATCH] powerpc: fix altivec_unavailable_exception Oopses

altivec_unavailable_exception is called without setting r3... it looks like
the r3 that actually gets passed in as struct pt_regs *regs is the
undisturbed value of r3 at the time the altivec instruction was encountered.
The user actually gets to choose the pt_regs printed in the Oops!

This fixes the oops by passing the correct pt_regs pointer to
altivec_unavailable_exception.

Signed-off-by: Alan Curry <pacman@TheWorld.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>