xtensa: drop empty platform_* functions from platforms

Provide missing default implementation for platform_init and drop copies
of default platform_init, platform_setup and platform_heartbeet from
platforms/*/setup.c
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/kernel/platform.c

@@ -26,6 +26,7 @@
  * (Please, refer to include/asm-xtensa/platform.h for more information)
  */
 
+_F(void, init, (bp_tag_t *first), { });
 _F(void, setup, (char** cmd), { });
 _F(void, restart, (void), { while(1); });
 _F(void, halt, (void), { while(1); });

arch/xtensa/platforms/iss/setup.c

@@ -23,10 +23,6 @@
 #include <platform/simcall.h>
 
 
-void __init platform_init(bp_tag_t* bootparam)
-{
-}
-
 void platform_halt(void)
 {
 	pr_info(" ** Called platform_halt() **\n");
@@ -38,6 +34,7 @@ void platform_power_off(void)
 	pr_info(" ** Called platform_power_off() **\n");
 	simc_exit(0);
 }
+
 void platform_restart(void)
 {
 	/* Flush and reset the mmu, simulate a processor reset, and
@@ -46,10 +43,6 @@ void platform_restart(void)
 	/* control never gets here */
 }
 
-void platform_heartbeat(void)
-{
-}
-
 static int
 iss_panic_event(struct notifier_block *this, unsigned long event, void *ptr)
 {

arch/xtensa/platforms/xtfpga/setup.c

@@ -57,22 +57,6 @@ void platform_restart(void)
 	/* control never gets here */
 }
 
-void __init platform_setup(char **cmdline)
-{
-}
-
-/* early initialization */
-
-void __init platform_init(bp_tag_t *first)
-{
-}
-
-/* Heartbeat. */
-
-void platform_heartbeat(void)
-{
-}
-
 #ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
 
 void __init platform_calibrate_ccount(void)