samples: bluetooth: add overlays for RV32M1 SoC for BLW SW LL

Add the required specific HW configuration for SW defined
BLE LL on RV32M1 SoC, by means of DTS overlays:
- enable INTMUX0 channels 2 & 3
- route Generic FSK RF0 interrupt to INTMUX channel 3
- route LPTMR1 interrupt to INTMUX channel 2

This change is done for all Bluetooth samples that are intended to
run on RV32M1 using BLE SW LL.

Signed-off-by: George Stefan <george.stefan@nxp.com>
Signed-off-by: Radu Alexe <radu.alexe@nxp.com>
Signed-off-by: Ionut Ursescu <ionut.ursescu@nxp.com>
Signed-off-by: Alex Porosanu <alexandru.porosanu@nxp.com>