dt-bindings: mailbox: fix incorrect gce.h file paths

A few *gce.h file paths are not in 'dt-bindings/gce/<chip>-gce.h'
format. To fix it, replace 'dt-binding' with 'dt-bindings'

Fixes: 0553fb51 ("dt-bindings: mailbox: add definition for mt8195")
Signed-off-by: Miles Chen <miles.chen@mediatek.com>
Link: https://lore.kernel.org/r/20210922070845.5108-1-miles.chen@mediatek.com


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