baremetal: make entry point _start instead of lkmc_start

I forgot why I did that. Let's try and see it blow up.

baremetal/arch/aarch64/no_bootloader/exit.S

@@ -2,7 +2,7 @@
 
 #include <lkmc.h>
 
-.global lkmc_start
-lkmc_start:
+.global _start
+_start:
     mov x0, 0
     bl _exit

baremetal/arch/aarch64/no_bootloader/gem5_exit.S

@@ -1,5 +1,5 @@
 #include <lkmc/m5ops.h>
 
-.global lkmc_start
-lkmc_start:
+.global _start
+_start:
     LKMC_M5OPS_EXIT_ASM

baremetal/arch/aarch64/no_bootloader/multicore_asm.S

@@ -5,8 +5,8 @@
 
 #include <lkmc.h>
 
-.global lkmc_start
-lkmc_start:
+.global _start
+_start:
     /* Reset spinlock. */
     mov x0, 0
     ldr x1, =.Lspinlock

baremetal/arch/aarch64/no_bootloader/semihost_exit.S

@@ -1,11 +1,11 @@
 /* https://cirosantilli.com/linux-kernel-module-cheat#semihosting
  *
- * Since our stack pointer is not setup, we justa allocate a memory
+ * Since our stack pointer is not setup, we just a allocate a memory
  * region to contain the semihosting arguments, which must be in memory.
  */
 
-.global lkmc_start
-lkmc_start:
+.global _start
+_start:
     mov x1, 0x26
     movk x1, 2, lsl 16
     ldr x2, =.Lsemihost_args

baremetal/arch/aarch64/no_bootloader/wfe_loop.S

@@ -2,7 +2,7 @@
 
 #include <lkmc/m5ops.h>
 
-.global lkmc_start
-lkmc_start:
+.global _start
+_start:
     wfe
-    b lkmc_start
+    b _start