v86d: Improve kernel dependency

Working with enabling SPDX, an issue was observerd where v86d wasn't rebuilding
when the kernel was changed from linux-yocto to linux-yocto-rt.

This is due to the code in sstatesig.py which was seeing the RRECOMMENDS on a
kernel module and ignoring the DEPENDS. The v86d is technically a kernel module
since it uses kernel header files.

There are two ways to address this, we could inherit the module-base class and
the dependency code does the correct thing. It appears the code doesn't look into
STAGING_KERNEL_DIR though and doesn't use the kernel sources. We can therefore drop
the DEPENDS and the code will the do the correct thing.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>