Fix build against xorg-server >= 1.20.

Patch taken from upstream:
https://cgit.freedesktop.org/xorg/driver/xf86-video-savage/commit/?id=0ece556daa8a88771b669d8104396abd9166d2d0

diff --git a/src/savage_driver.c b/src/savage_driver.c
index 58a294d..3cda923 100644
--- a/src/savage_driver.c
+++ b/src/savage_driver.c
@@ -2034,8 +2034,6 @@ static Bool SavagePreInit(ScrnInfoPtr pScrn, int flags)
     xf86DrvMsg(pScrn->scrnIndex, X_PROBED, "Detected current MCLK value of %1.3f MHz\n",
 	       mclk / 1000.0);
 
-    pScrn->maxHValue = 2048 << 3;	/* 11 bits of h_total 8-pixel units */
-    pScrn->maxVValue = 2048;		/* 11 bits of v_total */
     pScrn->virtualX = pScrn->display->virtualX;
     pScrn->virtualY = pScrn->display->virtualY;
 
@@ -3637,6 +3635,14 @@ static ModeStatus SavageValidMode(SCRN_ARG_TYPE arg, DisplayModePtr pMode,
        (pMode->VDisplay > psav->PanelY)))
 	    return MODE_PANEL;
 
+    /* 11 bits of h_total 8-pixel units */
+    if (pMode->HTotal > (2048 << 3))
+	return MODE_BAD_HVALUE;
+
+    /* 11 bits of v_total */
+    if (pMode->VTotal > 2048)
+	return MODE_BAD_VVALUE;
+
     if (psav->UseBIOS) {
 	refresh = SavageGetRefresh(pMode);
         return (SavageMatchBiosMode(pScrn,pMode->HDisplay,
overy.scm?id=c20426ec5cdb846f1f1416942a055651a2a3cb65'>tree</a><a href='/guix/commit/tests/discovery.scm?id=c20426ec5cdb846f1f1416942a055651a2a3cb65'>commit</a><a href='/guix/diff/tests/discovery.scm?id=c20426ec5cdb846f1f1416942a055651a2a3cb65'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/tests/discovery.scm'>
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<div class='path'>path: <a href='/guix/log/?id=c20426ec5cdb846f1f1416942a055651a2a3cb65'>root</a>/<a href='/guix/log/tests?id=c20426ec5cdb846f1f1416942a055651a2a3cb65'>tests</a>/<a href='/guix/log/tests/discovery.scm?id=c20426ec5cdb846f1f1416942a055651a2a3cb65'>discovery.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/discovery.scm?id=c20426ec5cdb846f1f1416942a055651a2a3cb65&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2017-07-03 23:51:23 +0200'>2017-07-03</span></td><td><a href='/guix/commit/tests/discovery.scm?id=960c6ce96d746cf19829ad26e092ec5dad2a5c62'>discovery: Recurse into directories pointed to by a symlink.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>