Kernel: Add helper to map pages with base address and size

This allows us to easily map enough pages for buffer with known size

VESA driver can now allocate enough memory for whole framebuffer if it
doesn't fit in a single page (1920x1080 for example)

kernel/arch/i386/Paging.cpp

@@ -85,4 +85,11 @@ namespace Paging
 		asm volatile("invlpg (%0)" :: "r"(address) : "memory");
 	}
 
+	void MapPages(uintptr_t address, size_t size)
+	{
+		address = (address >> 21) << 21;
+		for (size_t offset = 0; offset < size; offset += 1 << 21)
+			MapPage(address + offset);
+	}
+
 }

kernel/arch/i386/VESA.cpp

@@ -98,7 +98,7 @@ namespace VESA
 		s_height	= framebuffer.height;
 		s_mode		= framebuffer.type;
 
-		Paging::MapPage(framebuffer.addr);
+		Paging::MapPages(s_addr, s_pitch * s_height);
 
 		if (s_mode == MULTIBOOT_FRAMEBUFFER_TYPE_GRAPHICS)
 		{