The doc varflag on UBOOT_CONFIG should be ignored by this code; without
this the recent addition of the UBOOT_CONFIG[doc] to documentation.conf
causes errors when UBOOT_MACHINE is used.
(From OE-Core rev: e41aa22d7938c200f4150155589f5e23ed0331ce)
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>