linux: import shared linux.inc so we have just one copy

* in my env I have 7 copies now
  ./meta-smartphone/meta-htc/recipes-kernel/linux/linux.inc
  ./meta-smartphone/meta-nokia/recipes-kernel/linux/linux.inc
  ./meta-smartphone/meta-openmoko/recipes-kernel/linux/linux.inc
  ./meta-smartphone/meta-samsung/recipes-kernel/linux/linux.inc
  ./meta-smartphone/meta-palm/recipes-kernel/linux/linux.inc
  ./meta-ti/recipes-kernel/linux/linux.inc
  ./meta-handheld/recipes-kernel/linux/linux.inc
  meta-smartphone's are 100% identical, meta-handheld is slightly
  different (ARM_KEEP_OABI can be set in recipe after require .inc) and
  meta-ti seems like much older version of linux.inc

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>