mtd: cmdlinepart: fix the overflow of big mtd partitions

When the kernel parses the following cmdline

	#mtdparts=gpmi-nand:16m(boot),16m(kernel),1g(home),4g(test),-(usr)

for a big nand chip Micron MT29F64G08AFAAAWP(8GB), we got the following wrong
result:

	.............................................
		"mtd: partition size too small (0)"
	.............................................

We can not get any partition.

The "4g(test)" partition triggers a overflow of the "size". The memparse()
returns 4g to the "size", but the size is "unsigned long" type, so a overflow
occurs, the "size" becomes zero in the end.

This patch changes the "size"/"offset" to "unsigned long long" type,
and replaces the UINT_MAX with ULLONG_MAX for macros SIZE_REMAINING and
OFFSET_CONTINUOUS.

Signed-off-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>