Currently, data in address space __memx is allocated to .progmem.data, i.e. the
same section as for __flash resp. progmem.  However, there os no need that
__memx goes onto the same section and wastes precious memory in the first 64 Ki.

The patch puts __memx data into .progmemx.data so that a linker script can
allocate it after .text and it can be distinguished from data in __flash or
progmem.

The current default linker script contains .progmem* so that the patch does not
change anything here.  A new default script is still to come (binutils PR14406).

Moreover, there is some code clean-up like avoid magic "6" and use
ADDR_SPACE_COUNT instead.

Ok to apply?

Johann


	PR target/55897
	* config/avr/avr.h (ADDR_SPACE_COUNT): New enum.
	(avr_addrspace_t): Add .section_name field.
	* config/avr/avr.c (progmem_section): Use ADDR_SPACE_COUNT as
	array size.
	(avr_addrspace): Same.  Initialize .section_name.  Remove last
	NULL entry.  Put __memx into .progmemx.data.
	(progmem_section_prefix): Remove.
	(avr_asm_init_sections): No need to initialize progmem_section.
	(avr_asm_named_section): Use avr_addrspace[].section_name to get
	section name prefix.
	(avr_asm_select_section): Ditto.  And use get_unnamed_section to
	retrieve the progmem section.
	* avr-c.c (avr_cpu_cpp_builtins): Use ADDR_SPACE_COUNT as loop
	boundary to run over avr_addrspace[].
	(avr_register_target_pragmas): Ditto.