bootloader: Restore activation of CR0 PAGING bit in init_page_directory.

Otherwise it may not be activated until much later.

May fix #20155.

src/system/boot/platform/bios_ia32/mmu.cpp

@@ -372,6 +372,7 @@ init_page_directory(void)
 	// switch to the new pgdir and enable paging
 	asm("movl %0, %%eax;"
 		"movl %%eax, %%cr3;" : : "m" (sPageDirectory) : "eax");
+	x86_write_cr0(x86_read_cr0() | CR0_PAGING);
 }