MIPS: AR7: Defer registration of GPIO

When called from prom init code, ar7_gpio_init() will fail as it will
call gpiochip_add() which relies on a working kmalloc() to alloc
the gpio_desc array and kmalloc is not useable yet at prom init time.

Move ar7_gpio_init() to ar7_register_devices() (a device_initcall)
where kmalloc works.

Fixes: 14e85c0e69 ("gpio: remove gpio_descs global array")
Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
Cc: Nicolas Schichan <nschichan@freebox.fr>
Cc: linux-mips@linux-mips.org
Cc: linux-serial@vger.kernel.org
Cc: <stable@vger.kernel.org> # 3.19+
Patchwork: https://patchwork.linux-mips.org/patch/17542/
Signed-off-by: James Hogan <jhogan@kernel.org>

arch/mips/ar7/platform.c

@@ -653,6 +653,10 @@ static int __init ar7_register_devices(void)
 	u32 val;
 	int res;
 
+	res = ar7_gpio_init();
+	if (res)
+		pr_warn("unable to register gpios: %d\n", res);
+
 	res = ar7_register_uarts();
 	if (res)
 		pr_err("unable to setup uart(s): %d\n", res);

arch/mips/ar7/prom.c

@@ -246,8 +246,6 @@ void __init prom_init(void)
 	ar7_init_cmdline(fw_arg0, (char **)fw_arg1);
 	ar7_init_env((struct env_var *)fw_arg2);
 	console_config();
-
-	ar7_gpio_init();
 }
 
 #define PORT(offset) (KSEG1ADDR(AR7_REGS_UART0 + (offset * 4)))