platform: aarch64: remove the platform_in_isr() helper

Added os_in_isr() helper in freertos environment for AARCH64
platforms, so remove the unused one.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>

lib/include/platform/aarch64/rpmsg_platform.h

@@ -39,7 +39,6 @@ int32_t platform_init_interrupt(uint32_t vector_id, void *isr_data);
 int32_t platform_deinit_interrupt(uint32_t vector_id);
 int32_t platform_interrupt_enable(uint32_t vector_id);
 int32_t platform_interrupt_disable(uint32_t vector_id);
-int32_t platform_in_isr(void);
 void platform_notify(uint32_t vector_id);
 
 /* platform low-level time-delay (busy loop) */

lib/rpmsg_lite/porting/platform/aarch64/rpmsg_platform.c

@@ -61,8 +61,6 @@ enum sw_mbox_channel_status {
     S_VALID,
 };
 
-extern uint64_t ullPortInterruptNesting;
-
 static int32_t disable_counter = 0;
 static void *platform_lock;
 #if defined(RL_USE_STATIC_API) && (RL_USE_STATIC_API == 1)
@@ -177,20 +175,6 @@ void platform_time_delay(uint32_t num_msec)
     }
 }
 
-/**
- * platform_in_isr
- *
- * Return whether CPU is processing IRQ
- *
- * @return True for IRQ, false otherwise.
- *
- */
-int32_t platform_in_isr(void)
-{
-    /* This is only working for FreeRTOS */
-    return (ullPortInterruptNesting > 0);
-}
-
 /**
  * platform_interrupt_enable
  *