configs/imx6ulz_bsh_smm_m2_defconfig: new defconfig

configs/imx6ulz_bsh_smm_m2_defconfig: new defconfig

BSH SMM M2 (SystemMaster M2) Board is an add-on board which provides
input and output interfaces to a dedicated carrier board. It is designed
mainly to provide graphical/video and connectivity interfaces to the
appliance.

Board support package includes the following components:
- mainline Linux kernel 6.1.68
- mainline U-Boot 2023.10

Signed-off-by: Michael Trimarchi <[email protected]>
Signed-off-by: Dario Binacchi <[email protected]>
Reviewed-by: Giulio Benetti <[email protected]>
Tested-by: Giulio Benetti <[email protected]>
[Romain:
  - enable BR2_DOWNLOAD_FORCE_CHECK_HASHES and add hashes files
  - enable BR2_KERNEL_HEADERS_AS_KERNEL for linux-headers to avoid specify
    BR2_KERNEL_HEADERS_6_1
  - make sure to use uuu from HOST_DIR in flash.sh
]
Signed-off-by: Romain Naour <[email protected]>