spi: core and gpio expanders use subsys_init

Make the SPI external GPIO expander drivers register themselves at
subsys_initcall() time when they're statically linked, and make the SPI
core do its driver model initialization earlier so that's safe.

SOC-integrated GPIOs are available starting very early -- often before
initcalls start to run, or earily in arch_initcall() at latest -- so this
improves consistency, letting more subsystems rely on GPIOs being usable
by their own subsys_initcall() code.

Signed-off-by: David Brownell <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/gpio/max7301.c

···
 {
 	return spi_register_driver(&max7301_driver);
 }
+/* register after spi postcore initcall and before
+ * subsys initcalls that may rely on these GPIOs
+ */
+subsys_initcall(max7301_init);
 
 static void __exit max7301_exit(void)
 {
 	spi_unregister_driver(&max7301_driver);
 }
-
-module_init(max7301_init);
 module_exit(max7301_exit);
 
 MODULE_AUTHOR("Juergen Beisert");

drivers/gpio/mcp23s08.c

···
 {
 	return spi_register_driver(&mcp23s08_driver);
 }
-module_init(mcp23s08_init);
+/* register after spi postcore initcall and before
+ * subsys initcalls that may rely on these GPIOs
+ */
+subsys_initcall(mcp23s08_init);
 
 static void __exit mcp23s08_exit(void)
 {

drivers/spi/spi.c

···
  * driver registration) _could_ be dynamically linked (modular) ... costs
  * include needing to have boardinfo data structures be much more public.
  */
-subsys_initcall(spi_init);
+postcore_initcall(spi_init);