kernel-yocto: only replace leading -I in include paths

kernel-yocto: only replace leading -I in include paths

We just want to remove the first '-I' in $d, hence removing the
g' of sed avoid changing the real path which is include '-I'

We also add an anchor to the regex to only match -I at the start
of the path.

Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>