driver core: make kobj_type constant.

This way instances of kobj_type (which contain function pointers) can be
stored in .rodata, which means that they cannot be [easily/accidentally]
modified at runtime.

Signed-off-by: Wedson Almeida Filho <wedsonaf@google.com>
Link: https://lore.kernel.org/r/20211224231345.777370-1-wedsonaf@google.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>