ARM: dts: aspeed: bletchley: Switch to spi-gpio for spi2

Switch spi2 to spi-gpio driver to avoid unstable signal issue with EVT
HW.

Remove spi2 node and create a new spi2_gpio node.

Signed-off-by: Potin Lai <potin.lai@quantatw.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Patrick Williams <patrick@stwcx.xyz>
Link: https://lore.kernel.org/r/20220215163151.32252-6-potin.lai@quantatw.com


Signed-off-by: Joel Stanley <joel@jms.id.au>