pico_cyw43_driver/cyw43_bus_pio_spi.c: make SPI_PROGRAM_NAME and CLOC…

[mvds00]

Fixes #1498

This patch allows to override the default value for SPI_PROGRAM_NAME and CLOCK_DIV in src/rp2_common/pico_cyw43_driver/cyw43_bus_pio_spi.c by defining CYW43_SPI_PROGRAM_NAME and/or CYW43_PIO_CLOCK_DIV.

This is useful when other cpu speeds are involved, e.g. running the Pi Pico W at 12 MHz from xosc.

[matsobdev]

It would be nice to have full range of cpu speeds at runtime for Pico W.

[mvds00]

I fully agree @matsobdev, the potential for power efficient applications is huge. But it involves a lot of changes. Running from xosc at 12 MHz with pll_sys disabled for example, is currently not possible using build settings alone. I think the first step in having the full range of cpu speeds available, would be to make the cpu speed and everything depending on it configurable at build time.

[ai6aj]

See also #1521 which allows the default clock divisor to be overridden at runtime, which is useful for Micropython etc. Both patches look like they can merge with each other without issue.