aarch64: morello: dynamic linking support

aarch64: morello: dynamic linking support

Add morello specific dl-machine.h.

Add morello dynamic relocation processing support for purecap ABI.
Only support R_AARCH64_NONE, R_AARCH64_ABS64 and R_AARCH64_RELATIVE
dynamic relocs from the lp64 ABI.

RELATIVE and IRELATIVE relocs use a helper function from cheri-rel.h
to construct a capability.  Also fixed the IRELATIVE handling for
static linking.

Use new machine routines on morello for load address computation so it
is a valid capability:

 void *elf_machine_runtime_dynamic (void)
 void elf_machine_rtld_base_setup (struct link_map *map, void *args)

The ld.so load address and RX, RW capabilities are derived from auxv
and the RW ranges are set up based on the ld.so program headers early.

__tls_get_addr should return a bounded pointer instead of fixing it in
_dl_make_tlsdesc_dynamic, this is done in a separate patch.