spi: Update clock-names property for arm pl022

PL022 has two input clocks named sspclk and apb_pclk. Current schema
refers to two notations of sspclk which are indeed same and thus one can
be dropped. Update clock-names property to reflect the same.

Signed-off-by: Kuldeep Singh <singh.kuldeep87k@gmail.com>
Link: https://lore.kernel.org/r/20220309171847.5345-1-singh.kuldeep87k@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>