spi: ath79: remove spi-master setup and cleanup assignment

This removes the assignment of setup and cleanup functions for the ath79
target. Assigning the setup-method will lead to 'setup_transfer' not
being assigned in spi_bitbang_init. Because of this, performing any
TX/RX operation will lead to a kernel oops.

Also drop the redundant cleanup assignment, as it's also assigned in
spi_bitbang_init.

Signed-off-by: David Bauer <mail@david-bauer.net>
Link: https://lore.kernel.org/r/20210303160837.165771-2-mail@david-bauer.net
Signed-off-by: Mark Brown <broonie@kernel.org>