Using `PROGRAMMER=bmp` has been proven to work reliably at least on
SAMD21, SAMD5x and SAML21.
Since using unsupported programmers is treated as a warning, this change
only reduces the noise in the shell a bit and is not a functional
change.
[1]: https://black-magic.org/supported-targets.html
This adds supoprt for the Atmel SAMD51 & SAME54 SoC.
The SAME5x/SAMD5x is a line of Cortex-M4F MCUs that share peripherals
with the samd2x Cortex-M0+ and saml1x Cortex-M23 parts.
