drm/i915: Set i9xx sdvo clock limits according to specifications

The Intel PRM says the M1 and M2 divisors must be in the range of 10-20 and 5-9.
Since we do all calculations based on them being register values (which are
subtracted by 2) we need to specify them accordingly.

Signed-off-by: Patrik Jakobsson <[e-mail]>
Reviewed-by: Chris Wilson <[e-mail]>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=56359
Cc: [e-mail]
Signed-off-by: Daniel Vetter <[e-mail]>

drivers/gpu/drm/i915/intel_display.c

···
 	.vco = { .min = 1400000, .max = 2800000 },
 	.n = { .min = 1, .max = 6 },
 	.m = { .min = 70, .max = 120 },
-	.m1 = { .min = 10, .max = 22 },
-	.m2 = { .min = 5, .max = 9 },
+	.m1 = { .min = 8, .max = 18 },
+	.m2 = { .min = 3, .max = 7 },
 	.p = { .min = 5, .max = 80 },
 	.p1 = { .min = 1, .max = 8 },
 	.p2 = { .dot_limit = 200000,