aarch64, Darwin: Improve Apple M3 cores, add M4

aarch64, Darwin: Improve Apple M3 cores, add M4

Complete the list of M3 cores (Ibiza, Palma and Lobos) and add the M4
cores (Donan and two types of Brava).

The values for chip IDs and the LITTLE.big variants have been taken from
lists in the XNU sources (xnu/osfmk/arm/cpuid.h) in xnu-11417.101.15.

gcc/ChangeLog:

	* config/aarch64/aarch64-cores.def (AARCH64_CORE): Improve Apple
	M3 and add Apple M4 cores.
	* config/aarch64/aarch64-tune.md: Regenerate.
	* doc/invoke.texi: Add apple-m4 core to the ones listed
	for arch and tune selections.