fix: made raspi2 compile

kernel/arch/arm/raspi2/start.s

@@ -7,6 +7,12 @@
 .section .text.boot
 _start:
     CPSID aif //Disable interrupts
+    //check if current cpu is cpu0
+1:
+    mrc p15, 0, r0, c0, c0, 5;
+    ands r0, #3
+    wfine
+    bne 1b
     ldr sp,  =svc_stack
     push {r0,r1,r2}
     //set other stacks

kernel/hw/raspi2/serial/serial.cpp

@@ -34,7 +34,7 @@ auto Serial::serial_puti(int i) -> void {
     char buf[65];
     char *ptr=buf+63;
     ptr[1]=0;
-    char *chars = "0123456789";
+    const char *chars = "0123456789";
     do {
         *(ptr--) = chars[i%10];
         i/=10;

kernel/hw/raspi2/uart/uart.cpp

@@ -1,7 +1,6 @@
 #include "uart.hpp"
-static volatile uint32_t x;
-auto delay = [&x](uint32_t count) {
-    for(x=0;x<count;x++);
+auto delay = [](uint32_t count) {
+    for(uint32_t x=0;x<count;x++);
 };
 UART &UART::getInstance() {
     static UART instance;