.gitignore: Add Doxygen dir `libflashrom-doc/`

Change-Id: Id25d05cdf6107cc7a99b94a8523e23bd8698c2d6
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/20811
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: David Hendricks <david.hendricks@gmail.com>
1 file changed