bluetooth: config: Fix bluetooth config dependencies

Fix bluetooth config dependencies where the definitions depend on other
definitions.
BT_RX_PRIO is not always defined in a controller only build.
BT_CTLR_TX_BUFFER_SIZE does not depend on BT_CTLR, but BT_LL_SW.

Signed-off-by: Joakim Andersson <joakim.andersson@nordicsemi.no>