uboot-phytec

kbuild: convert some make rules to Kbuild style

We can get Kbuild-ish log style like this:
  GEN     include/autoconf.mk
  GEN     include/autoconf.mk.dep

We do not need XECHO any more.

And also change checkstack target like Linux Kernel.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>