baremetal: fix heap and stack position in preparation for CLI arguments

baremetal/lib/aarch64.S

@@ -20,7 +20,7 @@ _start:
     isb
 
     /* Prepare the stack for main, mandatory for C code. */
-    ldr x0, =stack_top
+    ldr x0, =lkmc_stack_top
     mov sp, x0
 
     /* https://cirosantilli.com/linux-kernel-module-cheat#magic-failure-string */

baremetal/lib/arm.S

@@ -8,7 +8,7 @@ _start:
     bne lkmc_cpu_not_0
 
     /* Prepare the stack for main, mandatory for C code. */
-    ldr sp, =stack_top
+    ldr sp, =lkmc_stack_top
 
     /* Enable floating point.
      * Code copied from: http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0409h/CHDEGGFF.html

baremetal/lib/syscalls.c

@@ -12,8 +12,8 @@ enum {
     UART_FR_RXFE = 0x10,
 };
 
-extern char heap_low;
-extern char heap_top;
+extern char lkmc_heap_low;
+extern char lkmc_heap_top;
 
 char *heap_end = 0;
 
@@ -90,10 +90,10 @@ _CLOCK_T_ _times_r (struct _reent *r, struct tms *ptms) {
 caddr_t _sbrk(int incr) {
     char *prev_heap_end;
     if (heap_end == 0) {
-        heap_end = &heap_low;
+        heap_end = &lkmc_heap_low;
     }
     prev_heap_end = heap_end;
-    if (heap_end + incr > &heap_top) {
+    if (heap_end + incr > &lkmc_heap_top) {
         /* Heap and stack collision */
         return (caddr_t)0;
     }