Memory allocated by 'spi_alloc_master()' is already zeroed.
Remove a redundant memset.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/20200802175007.703995-1-christophe.jaillet@wanadoo.fr


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