RISC-V: hwprobe: sort EXT_KEY()s in hwprobe_isa_ext0() alphabetically

RISC-V: hwprobe: sort EXT_KEY()s in hwprobe_isa_ext0() alphabetically

Currently the entries appear to be in a random order (although according
to Palmer he has tried to sort them by key value) which makes it harder
to find entries in a growing list, and more likely to have conflicts as
all patches are adding to the end of the list. Sort them alphabetically
instead.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Clément Léger <cleger@rivosinc.com>
Link: https://lore.kernel.org/r/20240717-dedicate-squeamish-7e4ab54df58f@spud
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>