Kbuild: Fix board.h include issue on pentium BSP.

This commit fixes an issue with the inclusion path for the
board.h file for the pentium BSP.

Signed-off-by: Juan Manuel Cruz <juan.m.cruz.alcaraz@linux.intel.com>
Change-Id: I28172f8071b907aa61660ec8b8009e83cb2aa5ea
2 files changed