net: lwm2m: remove LWM2M_OP_NONE flag and renumber the rest

Remove unused OP flag LWM2M_OP_NONE and renumber the existing flags
so that the operations used in object permissions land in the lowest
bits, and extended operations come later.

We may eventually add more permission / data flags, so let's try and
keep them inside a 1 byte boundary (flags with bits 0 to 7).

NOTE: LWM2M_OP_DELETE is currently not checked as a permission but
it may be in the future so it is in the lower bits.

Signed-off-by: Michael Scott <michael@opensourcefoundries.com>