[ARM] fix sharp zaurus c-3000 compile failure without CONFIG_FB_PXA

This fixes compile problem when CONFIG_FB_PXA is not set.

  LD      .tmp_vmlinux1
arch/arm/mach-pxa/built-in.o(.text+0x1d74): In function
`spitz_get_hsync_len':
: undefined reference to `pxafb_get_hsync_time'
make: *** [.tmp_vmlinux1] Error 1
3.46user 0.46system 5.10 (0m5.106s) elapsed 77.01%CPU
Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-pxa/corgi_lcd.c

@@ -488,6 +488,7 @@ static int is_pxafb_device(struct device * dev, void * data)
 
 unsigned long spitz_get_hsync_len(void)
 {
+#ifdef CONFIG_FB_PXA
 	if (!spitz_pxafb_dev) {
 		spitz_pxafb_dev = bus_find_device(&platform_bus_type, NULL, NULL, is_pxafb_device);
 		if (!spitz_pxafb_dev)
@@ -496,6 +497,7 @@ unsigned long spitz_get_hsync_len(void)
 	if (!get_hsync_time)
 		get_hsync_time = symbol_get(pxafb_get_hsync_time);
 	if (!get_hsync_time)
+#endif
 		return 0;
 
 	return pxafb_get_hsync_time(spitz_pxafb_dev);