DRM: solve __linux__ missing on some toolchains

An ifdef in drm.h expects to be compiled with full-fledged Linux
toolchain, but it's common to compile kernel with just bare-metal
toolchain which doesn't define __linux__. So, also add __KERNEL__
check.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
1 file changed