baremetal aarch64: create C version of multicore.S as well

Attempted to do the same for arm, but it failed.

baremetal/arch/arm/no_bootloader/multicore_asm.S

@@ -0,0 +1,40 @@
+/* https://cirosantilli.com/linux-kernel-module-cheat#arm-multicore */
+
+#include <lkmc.h>
+
+.global lkmc_start
+lkmc_start:
+    mov r0, 0
+    ldr r1, =.Lspinlock
+    str r0, [r1]
+    /* Get CPU ID. */
+    mrc p15, 0, r1, c0, c0, 5
+    ands r1, r1, 3
+    beq .Lcpu0_only
+.Lcpu1_only:
+    mov r0, 1
+    ldr r1, =.Lspinlock
+    str r0, [r1]
+    dmb sy
+    sev
+.Lcpu1_sleep_forever:
+    wfe
+    b .Lcpu1_sleep_forever
+.Lcpu0_only:
+#if !LKMC_GEM5
+    /* PSCI CPU_ON. */
+    ldr r0, =0x84000003
+    mov r1, 1
+    ldr r2, =.Lcpu1_only
+    mov r3, 0
+    hvc 0
+#endif
+.Lspinlock_start:
+    ldr r0, .Lspinlock
+    wfe
+    cmp r0, 0
+    beq .Lspinlock_start
+    mov r0, 0
+    bl _exit
+.Lspinlock:
+    .skip 4