u-boot: 2015.07 - fix creation of .config

u-boot: 2015.07 - fix creation of .config

Due to recent changes in U-Boot, see
http://git.denx.de/?p=u-boot.git;a=commit;h=a26cd04920dc069fd6e91abb785426cf6c29f45f
re-creation of .config from defconfig by "make oldconfig" happened
incorrectly.

Default prompt for target selection was set as No that lead to missing platform
selection by automated scripts like that:
------------------>8------------------
"yes "" | make oldconfig" on defconfig
------------------>8------------------

And that lead to build failure:
------------------>8------------------
$ make
scripts/kconfig/conf --silentoldconfig Kconfig
  CHK     include/config.h
  UPD     include/config.h
  GEN     include/autoconf.mk
In file included from ./include/common.h:18:0:
include/config.h:5:22: fatal error: configs/.h: No such file or directory
 #include <configs/.h>
                      ^
compilation terminated.
scripts/Makefile.autoconf:72: recipe for target 'include/autoconf.mk' failed
make[1]: *** [include/autoconf.mk] Error 1
------------------>8------------------

This patch reverts mentioned change making possible to build U-Boot
2015.07 in Buildroot.

Note there's a probability that this particular patch won't make its way
in upstream U-Boot and better solution will be found there. But for now
we need to fix U-Boot building in Buildroot anyways.

Hopefully for the next release this patch won't be necessary.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>