**Problems**
`SPIMaster` pad names are `clk`, `cs_n`, `mosi`, and `miso`.
However, `feather_spi` is using `sck` instead of `clk`, therefore
it is not able to use as-is for `SPIMaster`, for example,
with `add_spi` on Linux On LiteX VexRiscv.
**Solution**
In fact, `spisdcard` and other SPI related pad names are
using `clk`, only `feather_spi` is using `sck`.
Therefore, rename `sck` to `clk`.