linux-yocto: add bc-native dependency, and move to linux-yocto.inc

linux-yocto: add bc-native dependency, and move to linux-yocto.inc

As reported by Martin Jansa <martin.jansa@gmail.com>, the following error happens
when building in a minimal environment:

   |   BC      kernel/timeconst.h
   | /bin/sh: bc: command not found
   | make[3]: *** [kernel/timeconst.h] Error 127
   | make[2]: *** [kernel] Error 2
   | make[2]: *** Waiting for unfinished jobs....

kernel commit 70730bca [kernel: Replace timeconst.pl with a bc script] added
a kernel dependency on bc. To support the build of linux-yocto recipes in
these configurations, we add bc-native to the common dependencies.

(From OE-Core rev: c888857b060f04b8689f393ec2d77a950da40f5a)

Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>