stm32: add new stm32 target
New stm32 target introduces support for stm32mp1 based devices.
For now it includes an initial support of the STM32MP135F-DK device.
The specifications bellow only list supported features.
Specifications
--------------
SOC: STM32MP135FAF7
RAM: 512 MiB
Storage: SD Card
Ethernet: 2x 100 Mbps
Wireless: 2.4GHz Cypress CYW43455 (802.11b/g/n)
LEDs: Heartbeat (Blue)
Buttons: 1x Reset, 1x User (USER2)
USB: 4x 2.0 Type-A
Signed-off-by: Thomas Richard <thomas.richard@bootlin.com>
Link: https://github.com/openwrt/openwrt/pull/16716
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>