FRV: Correctly determine the address of an illegal instruction

Correctly determine the address of an illegal instruction.  The EPCR0 register
holds this value (masked by EPCR0_PC) if the validity bit is set (masked by
EPCR0_V).  So the test as to whether the contents of the register are usable
should be involve checking the _V bit, not the _PC bits.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>