[yocto] include all kernel modules in image

[Trevor Woerner]

Hey Nicolas,

Thanks for taking a poke at this and for verifying it should otherwise
work ;-)

It turns out it was a version issue (as I suspected), the "-rc1" should
have been in a variable named "LINUX_VERSION_EXTENSION" leaving the rest
in "LINUX_VERSION" as before:

    SRC_URI =
"git://github.com/TeeFirefly/linux-rockchip.git;branch=firefly;rev=cbbae6741c60c9e09f87521e3a79810abd6a2fda"
    LINUX_VERSION ?= "4.0.0"
    LINUX_VERSION_EXTENSION = "-rc1"

Best regards,
    Trevor