Squashed commit of the following:
Change all remaining occurrences of SAMDL to SAMD2L2.
configs/: Change all remaining occurrences of SAMDL to SAMD2L2
configs/: Change all occurrences of CONFIG_SAMDL_* to CONFIG_SAMD2L2_*
arch/arm/src and include: Rename all directories from samdl to samd2l2. Change all configuration variable names and other usage from SAMDL to SAMD2L2.
Squashed commit of the following:
configs/*/README.txt: Replace each occurrence of './configure.sh' with 'tools/configure.sh'
configs/*/README.txt: Remove 'cd ..' after each './configure.sh'
configs/*/README.txt: Remove 'cd -' after each './configure.sh'
configs/*/README.txt: Remove 'cd tools' before each './configure.sh'
configs/README.txt: Remove instruction to CD tools/ before running configure.sh.