video: fbdev: sis: Fix set but not used warnings in sis_main

Fix warnings by dropping unused variable and the
unused assignments.

v2:
  - Update subject (Lee)
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Thomas Winischhofer <thomas@winischhofer.net>
Cc: Lee Jones <lee.jones@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201128224114.1033617-11-sam@ravnborg.org

drivers/video/fbdev/sis/sis_main.c

@@ -5029,7 +5029,6 @@ static void sisfb_post_xgi_ddr2(struct sis_video_info *ivideo, u8 regb)
 	static const u8 cs168[8] = {
 		0x48, 0x78, 0x88, 0x00, 0x00, 0x00, 0x00, 0x00
 	};
-	u8 reg;
 	u8 v1;
 	u8 v2;
 	u8 v3;
@@ -5037,9 +5036,9 @@ static void sisfb_post_xgi_ddr2(struct sis_video_info *ivideo, u8 regb)
 	SiS_SetReg(SISCR, 0xb0, 0x80); /* DDR2 dual frequency mode */
 	SiS_SetReg(SISCR, 0x82, 0x77);
 	SiS_SetReg(SISCR, 0x86, 0x00);
-	reg = SiS_GetReg(SISCR, 0x86);
+	SiS_GetReg(SISCR, 0x86);
 	SiS_SetReg(SISCR, 0x86, 0x88);
-	reg = SiS_GetReg(SISCR, 0x86);
+	SiS_GetReg(SISCR, 0x86);
 	v1 = cs168[regb]; v2 = cs160[regb]; v3 = cs158[regb];
 	if (ivideo->haveXGIROM) {
 		v1 = bios[regb + 0x168];
@@ -5049,9 +5048,9 @@ static void sisfb_post_xgi_ddr2(struct sis_video_info *ivideo, u8 regb)
 	SiS_SetReg(SISCR, 0x86, v1);
 	SiS_SetReg(SISCR, 0x82, 0x77);
 	SiS_SetReg(SISCR, 0x85, 0x00);
-	reg = SiS_GetReg(SISCR, 0x85);
+	SiS_GetReg(SISCR, 0x85);
 	SiS_SetReg(SISCR, 0x85, 0x88);
-	reg = SiS_GetReg(SISCR, 0x85);
+	SiS_GetReg(SISCR, 0x85);
 	SiS_SetReg(SISCR, 0x85, v2);
 	SiS_SetReg(SISCR, 0x82, v3);
 	SiS_SetReg(SISCR, 0x98, 0x01);