drm/mgag200: make a const array static, makes object smaller

Don't populate the const array m_div_val on the stack but instead make
it static. Makes the object code smaller by 29 bytes:

Before:
   text	   data	  bss   dec    hex filename
  34736	   4552	    0 39288   9978 drivers/gpu/drm/mgag200/mgag200_mode.o

After:
   text	   data	  bss   dec    hex filename
  34625	   4616	    0 39241   9949 drivers/gpu/drm/mgag200/mgag200_mode.o

(gcc version 10.2.0)
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20210204191156.110778-1-colin.king@canonical.com

drivers/gpu/drm/mgag200/mgag200_mode.c

@@ -706,13 +706,13 @@ static int mga_g200eh_set_plls(struct mga_device *mdev, long clock)
 
 static int mga_g200er_set_plls(struct mga_device *mdev, long clock)
 {
+	static const unsigned int m_div_val[] = { 1, 2, 4, 8 };
 	unsigned int vcomax, vcomin, pllreffreq;
 	unsigned int delta, tmpdelta;
 	int testr, testn, testm, testo;
 	unsigned int p, m, n;
 	unsigned int computed, vco;
 	int tmp;
-	const unsigned int m_div_val[] = { 1, 2, 4, 8 };
 
 	m = n = p = 0;
 	vcomax = 1488000;