[PATCH] i810fb: Change option ext_vga to extvga to match documentation

Reported by: Manuel Lauss <mano@roarinelk.homelinux.net>

He was getting random initial video modes depending on the kernel
configuration.  His option line includes 'extvga'.

The i810fb documentation describes the option 'extvga', however the
driver accepts 'ext_vga'.  Besides 'extvga' being ignored by i810fb,
it also confuses the option parser of i810fb and assigns 'extvga' to
'mode_option'.  This leads to an incorrect video mode at boot time.

Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>