args: increase major:minor limit to 4095:1048575

args: increase major:minor limit to 4095:1048575

Remove the limit for major and minor number arguments used while specifying
persistent numbers via -My --major <major> --minor <minor> option which
was set to 255 before. Follow the kernel limit instead which is 12 bits
for major and 20 bits for minor number (kernel >= 2.6 and LVM formats
that does not have FMT_RESTRICTED_LVIDS - so still keep the old limit
of 255 for lvm1 format).