dt-bindings: timer: sprd-timer: convert to YAML

Convert the Spreadtrum SC9860 timer bindings to DT schema.

Changes during conversion:
  - rename file to match compatible
  - add sprd,sc9860-suspend-timer which was previously undocumented
  - minor grammar fix in description

Signed-off-by: Stanislav Jakubek <stano.jakubek@gmail.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Link: https://lore.kernel.org/r/ZoU95lBgoyF/8Md3@standask-GA-A55M-S2HP


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