arch: arm: cortex_m: Move bss/noinit sections to the end of linker script

This results in a smaller binary with CONFIG_XIP=n as these NOLOAD
sections can be excluded.

bss/noinit have been included in CONFIG_XIP=n binaries by default since
c107827b. This also occurs if using
iterable sections or adding code/data to ITCM/DTCM sections.
Moving bss/noinit to the end of the linker file should ensure they are
always excluded

Signed-off-by: Grant Ramsay <gramsay@enphaseenergy.com>