Pass include directories to C preprocessor
Pass include directories to C preprocessor

If we include a header file within board/daisy/board.h then the code in the
top-level Makefile which transforms the configuration into make variables
cannot locate the header file. We get a warning:

$ make BOARD=daisy clean
board/daisy/board.h:11:20: fatal error: common.h: No such file or directory
compilation terminated.

To fix this, pass the include directories to the preprocessor also.

BUG=none
TEST=manual:
add common.h header to board/daisy/board.h; make BOARD=daisy clean;
see that no warning is issued

Change-Id: I04b718e014490a3f6008b7d03afce4d79a38eb56
Signed-off-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>

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