[PATCH] mtd cmdlinepart: allow zero offset value

Current cmdlinepart.c uses offset value 0 to specify a continuous
partition.  This prevents creating a second partition starting at 0.

For example, I can split 4MB device using "mtdparts=id:2M,2M", but I can
not do "mtdparts=id:2M@2M,2M@0" to swap mtd0 and mtd1.

This patch introduces special OFFSET_CONTINUOUS value for a continuous
partition and allows 0 for offset value.

Also this patch replaces 0xffffffff with UINT_MAX for SIZE_REMAINING.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Cc: Thomas Gleixner <tglx@linutronix.de>
Acked-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>