[IA64] always map VGA framebuffer UC, even if it supports WB

EFI on some machines, e.g., Intel Tiger, reports that the VGA framebuffer
supports WB access.  ioremap() prefers WB when possible, so it can work
when mapping main memory.

But it doesn't make sense to map a framebuffer WB, because the driver
doesn't flush explicitly, so updates won't make it to the device
immediately.

This is due to Zou Nan hai <nanhai.zou@intel.com>.

More extensive fix that adds a "size" argument coming soon.
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Tony Luck <tony.luck@intel.com>

include/asm-ia64/vga.h

@@ -17,7 +17,7 @@
 extern unsigned long vga_console_iobase;
 extern unsigned long vga_console_membase;
 
-#define VGA_MAP_MEM(x)	((unsigned long) ioremap(vga_console_membase + (x), 0))
+#define VGA_MAP_MEM(x)	((unsigned long) ioremap_nocache(vga_console_membase + (x), 0))
 
 #define vga_readb(x)	(*(x))
 #define vga_writeb(x,y)	(*(y) = (x))