Bluetooth: L2CAP: Fix sending MPS that cannot be fully used
Bluetooth: L2CAP: Fix sending MPS that cannot be fully used

MPS shall never be bigger than MTU + 2 as the remaining bytes cannot
be used since the SDU is limited to length + MTU.

Signed-off-by: Luiz Augusto von Dentz <8530c5ea66a1bdbc08f98bfcf183c8be901b5990@intel.com>

mbolivar/zephyr,finikorg/zephyr,zephyriot/zephyr,punitvara/zephyr,Vudentz/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,nashif/zephyr,zephyriot/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,aceofall/zephyr-iotos,finikorg/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,fbsder/zephyr,ldts/zephyr,Vudentz/zephyr,punitvara/zephyr,galak/zephyr,mbolivar/zephyr,punitvara/zephyr,mbolivar/zephyr,zephyrproject-rtos/zephyr,fbsder/zephyr,nashif/zephyr,zephyriot/zephyr,aceofall/zephyr-iotos,kraj/zephyr,fbsder/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,punitvara/zephyr,zephyriot/zephyr,mbolivar/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,ldts/zephyr,explora26/zephyr,zephyriot/zephyr,galak/zephyr,nashif/zephyr,aceofall/zephyr-iotos,Vudentz/zephyr,fbsder/zephyr,mbolivar/zephyr,explora26/zephyr,explora26/zephyr,galak/zephyr,aceofall/zephyr-iotos,Vudentz/zephyr,Vudentz/zephyr,kraj/zephyr,zephyrproject-rtos/zephyr,fbsder/zephyr,finikorg/zephyr,kraj/zephyr,nashif/zephyr,ldts/zephyr,finikorg/zephyr,aceofall/zephyr-iotos,zephyrproject-rtos/zephyr,finikorg/zephyr