[Committed] arm: Document +no options for Cortex-M55 CPU.

[Committed] arm: Document +no options for Cortex-M55 CPU.

This patch documents the following options for Arm Cortex-M55 CPU
under -mcpu= list.

+nomve.fp (disables MVE single precision floating point instructions)
+nomve (disables MVE integer and single precision floating point instructions)
+nodsp (disables dsp, MVE integer and single precision floating point instructions)
+nofp (disables floating point instructions)
Committed as obvious to master.

gcc/ChangeLog:

2022-08-12  Srinath Parvathaneni  <srinath.parvathaneni@arm.com>

	* doc/invoke.texi (Arm Options): Document -mcpu=cortex-m55 options.