meson: Add libdrm dependency for intel_drv

Looks like we need a libdrm dep on intel_drv. Build fails for me on
Arch.

In file included from ../src/intel_device.c:51:
/usr/include/xf86drm.h:40:10: fatal error: drm.h: No such file or directory
 #include <drm.h>

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>