spi: amd: Fix speed selection

spi: amd: Fix speed selection

If the current speed is equal to the requested speed by the device
then return success.
This patch fixes a bug introduced by the commit 3fe26121dc3a
("spi: amd: Configure device speed") which checks speed_hz instead
of amd_spi->speed_hz.

Fixes: 3fe26121dc3a ("spi: amd: Configure device speed")
Signed-off-by: Shreeya Patel <shreeya.patel@collabora.com>
Link: https://lore.kernel.org/r/20220830093607.45484-1-shreeya.patel@collabora.com
Signed-off-by: Mark Brown <broonie@kernel.org>