powerpc/mpic: Remove duplicate MPIC_WANTS_RESET flag

There are two separate flags controlling whether or not the MPIC is
reset during initialization, which is completely unnecessary, and only
one of them can be specified in the device tree.

Also, most platforms in-tree right now do actually want to reset the
MPIC during initialization anyways, which means lots of duplicate code
passing the MPIC_WANTS_RESET flag.

Fix all of the callers which currently do not pass the MPIC_WANTS_RESET
flag to pass the MPIC_NO_RESET flag, then remove the MPIC_WANTS_RESET
flag and make the code reset the MPIC by default.

Signed-off-by: Kyle Moffett <Kyle.D.Moffett@boeing.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>