net: lwm2m: Kconfig: move RD_CLIENT settings above dependencies

LwM2M boostrap support is enabled via the config option:
LWM2M_RD_CLIENT_SUPPORT_BOOTSTRAP.  If enabled, this config sets
the default # of server and security instances.  However, this is
not working correctly because LWM2M_RD_CLIENT_SUPPORT_BOOTSTRAP
is defined below it's uses in the Kconfig file.

Let's move the RD_CLIENT configs higher in the Kconfig to fix this
behavior.

Signed-off-by: Michael Scott <mike@foundries.io>