webkit-efl: inherit perlnative and s/ARM/arm/g in ARM_INSTRUCTION_SET

* ARM_INSTRUCTION_SET != "thumb" is enough but better to unify with
  other recipes in case someone does ARM_INSTRUCTION_SET == "arm" later

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>