drm/nouveau/bios: fix a bit shift error introduced by a8f030c

drm/nouveau/bios: fix a bit shift error introduced by a8f030c

Commit a8f030ca28456dd390df0a7207d0b654239b5cf5 added two checks applied to a
value received from nv_rd32(bios, 0x619f04). But after this new piece of code
is executed, the addr local variable does not hold the same value it used to
hold before the commit. Here is what is was assigned in the original code:
	(u64)(nv_rd32(bios, 0x619f04) & 0xffffff00) << 8
in the committed code it ends up with this value:
	(u64)(nv_rd32(bios, 0x619f04) >> 8) << 8
These expressions are obviously not equivalent.

My Nvidia video card does not show anything on the display when I boot a
kernel containing this commit.

The patch fixes the code so that the new checks are still done, but the
side effect of an incorrect addr value is gone.

Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sergei Antonov <saproj@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>