As RPL Root, drop an incoming DIO from the same instance but different DAG
cc2538: Generate .hex output

ELF files generated by GCC make SmartRF Flash Programmer 2 crash (only the TI
format is supported by this tool for ELFs), and binary files are not very
appropriate because they are gapless, so generate Intel HEX files since these
are very well supported by most programming tools while still flexible.

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
cc2538: Make it possible to use a custom linker script

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
cc2538dk: Make it possible to override UIP_CONF_TCP_MSS

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
cc2538: sys_ctrl: Make it possible to use the 32-kHz crystal

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
Merge pull request #406 from cetic/hotfix-rplroot-discard-dio

Drop incoming DIO when RPL Root
Merge pull request #413 from ADVANSEE/cc2538-build

cc2538: Various build improvements
Merge pull request #410 from ADVANSEE/cc2538-sys_ctrl

cc2538: sys_ctrl: Make it possible to use the 32-kHz crystal