i965: Move intel_debug.h to intel/common/gen_debug.h

i965: Move intel_debug.h to intel/common/gen_debug.h

This is shared between the Vulkan and GL drivers as it's a requirement
of the back-end compiler.  However, it doesn't really belong in the
compiler.  We rename the file to match the prefix of the other stuff in
common and because libdrm defines an intel_debug.h and this avoids a
pile of possible name conflicts.

Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>