SM501: reverse FPEN/VBIASEN flags behaviour

To keep backwards compatibility, reverse the meanings of these flags so
that when they are not set, the driver uses the original behvaiour.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Cc: Arnaud Patard <arnaud.patard@rtp-net.org>
Acked-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>