Kernel: Make the page table for the kernel image larger

Building the x86_64 kernel with ENABLE_EXTRA_KERNEL_DEBUG_SYMBOLS
results in an image that is larger than 0x2000000 bytes.

Kernel/Sections.h

@@ -12,7 +12,7 @@
 #define UNMAP_AFTER_INIT NEVER_INLINE __attribute__((section(".unmap_after_init")))
 
 #define KERNEL_BASE 0xC0000000
-#define KERNEL_PD_OFFSET 0x2000000
+#define KERNEL_PD_OFFSET 0x3000000
 #define KERNEL_PD_END 0xF1000000
 #define KERNEL_PT1024_BASE 0xFFE00000
 #define KERNEL_QUICKMAP_PT (KERNEL_PT1024_BASE + 0x6000)