viafb: reset correct PLL

Looks like we did reset the PLL of the (whatever) engine instead of
the PLL of the secondary display (IGA2, LCDCK). This patch fixes it.
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Cc: Joseph Chan <JosephChan@via.com.tw>

drivers/video/via/hw.c

@@ -1688,8 +1688,8 @@ void viafb_set_vclock(u32 clk, int set_iga)
 	}
 
 	if (set_iga == IGA2) {
-		viafb_write_reg_mask(SR40, VIASR, 0x01, BIT0);
-		viafb_write_reg_mask(SR40, VIASR, 0x00, BIT0);
+		viafb_write_reg_mask(SR40, VIASR, 0x04, BIT2);
+		viafb_write_reg_mask(SR40, VIASR, 0x00, BIT2);
 	}
 
 	/* Fire! */