build: add more implementers IDs and PNs for ARM

build: add more implementers IDs and PNs for ARM

1) Add native PN option '-march=native' to allow automatic detection.
   Set 'arm_force_native_march' to 'true' in config/arm/meson.build
   to use native PN option.
2) Add implementer_pn option for part num selection in cross compile
3) Add known Arm cortex PN support
4) Add known implementers' IDs (use generic flags/archs by default)
5) Sync build options with config/common_armv8a_linuxapp

Signed-off-by: Herbert Guan <herbert.guan@arm.com>
Acked-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>