inmates: arm: uart-demo: move heartbeat to header file

Moving the heartbeat function to a header file, so we can reuse
the uart-demo just by reimplementing the heartbeat on AArch64.

inmates/demos/arm/uart-demo.c

@@ -12,19 +12,6 @@
 
 #include <inmate.h>
 
-/*
- * To ease the debugging, we can send a spurious hypercall, which should return
- * -ENOSYS, but appear in the hypervisor stats for this cell.
- */
-static void heartbeat(void)
-{
-	asm volatile (
-	".arch_extension virt\n"
-	"mov	r0, %0\n"
-	"hvc	#0\n"
-	: : "r" (0xbea7) : "r0");
-}
-
 void inmate_main(void)
 {
 	unsigned int i = 0, j;

inmates/lib/arm/include/inmate.h

@@ -36,6 +36,19 @@ static inline void mmio_write32(void *address, u32 value)
 	*(volatile u32 *)address = value;
 }
 
+/*
+ * To ease the debugging, we can send a spurious hypercall, which should return
+ * -ENOSYS, but appear in the hypervisor stats for this cell.
+ */
+static inline void heartbeat(void)
+{
+	asm volatile (
+	".arch_extension virt\n"
+	"mov	r0, %0\n"
+	"hvc	#0\n"
+	: : "r" (0xbea7) : "r0");
+}
+
 void __attribute__((interrupt("IRQ"))) __attribute__((used)) vector_irq(void);
 
 typedef void (*irq_handler_t)(unsigned int);