dt-bindings: firmware: amlogic,scpi: Move arm,scpi-shmem to json schema

"amlogic,meson-gxbb-scp-shmem" is already in the Generic on-chip SRAM
binding though "amlogic,meson-gxbb-scpi" is missing which is now added.
Also remove the whole old text format binding for the same.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Kevin Hilman <khilman@baylibre.com>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Cc: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Link: https://lore.kernel.org/r/20210601224904.917990-5-sudeep.holla@arm.com


Signed-off-by: Rob Herring <robh@kernel.org>