block: move the *_PARTITION enum out of genhd.h

The enum containing the *_PARTITION symbolic names is only relevant
for the partition parser.  More specifically most values are MSDOS
partition table system indicators and thus should go straight into
msdos.c.  One value is only used by the sun partition parser, and the
sun and sgi partition parsers use the same value as the x86 Linux
RAID indicator to also indicate RAID autodetection.  Duplicate them
in sun.c and sgi.c given that the different partition types use
entirely different values otherwise.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>