spi: stm32: Revert "properly handle 0 byte transfer"

0 byte transfer handling is now done within the core in code added
by commit b3063203 ("spi: Skip zero-length transfers in spi_transfer_one_message()")

This reverts commit 2269f5a8 ("spi: stm32: properly handle 0 byte transfer")

Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
Link: https://lore.kernel.org/r/1625646426-5826-5-git-send-email-alain.volmat@foss.st.com


Signed-off-by: Mark Brown <broonie@kernel.org>