drm/i915: fix build with missing debugfs includes

/home/airlied/devel/kernel/dim/src/drivers/gpu/drm/i915/i915_debugfs_params.c:213:9: error: call to undeclared function 'debugfs_create_file_unsafe'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
        return debugfs_create_file_unsafe(name, mode, parent, value,
               ^
/home/airlied/devel/kernel/dim/src/drivers/gpu/drm/i915/i915_debugfs_params.c:213:9: error: incompatible integer to pointer conversion returning 'int' from a function with result type 'struct dentry *' [-Wint-conversion]
        return debugfs_create_file_unsafe(name, mode, parent, value,
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/airlied/devel/kernel/dim/src/drivers/gpu/drm/i915/i915_debugfs_params.c:222:9: error: call to undeclared function 'debugfs_create_file_unsafe'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
        return debugfs_create_file_unsafe(name, mode, parent, value,
               ^
/home/airlied/devel/kernel/dim/src/drivers/gpu/drm/i915/i915_debugfs_params.c:222:9: error: incompatible integer to pointer conversion returning 'int' from a function with result type 'struct dentry *' [-Wint-conversion]
        return debugfs_create_file_unsafe(name, mode, parent, value,
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Building with clang gave me a bunch of similiar fails to the above.

Fixes: 33d5ae6c

 ("drm/print: drop include debugfs.h and include where needed")
Signed-off-by: Dave Airlie <airlied@redhat.com>