PM / devfreq: rockchip-dfi: Handle LPDDR2 correctly

According to the downstream driver the DDRMON_CTRL_LPDDR23 bit must be
set for both LPDDR2 and LPDDR3. Add the missing LPDDR2 case and while
at it turn the if/else if/else into switch/case which makes it easier
to read.

Link: https://lore.kernel.org/all/[e-mail]/
Reviewed-by: Jonathan Cameron <[e-mail]>
Reviewed-by: Sebastian Reichel <[e-mail]>
Acked-by: Chanwoo Choi <[e-mail]>
Signed-off-by: Sascha Hauer <[e-mail]>
Signed-off-by: Chanwoo Choi <[e-mail]>

drivers/devfreq/event/rockchip-dfi.c

···
 		       DDRMON_CTRL_HARDWARE_EN), dfi_regs + DDRMON_CTRL);
 
 	/* set ddr type to dfi */
-	if (dfi->ddr_type == ROCKCHIP_DDRTYPE_LPDDR3)
+	switch (dfi->ddr_type) {
+	case ROCKCHIP_DDRTYPE_LPDDR2:
+	case ROCKCHIP_DDRTYPE_LPDDR3:
 		writel_relaxed(HIWORD_UPDATE(DDRMON_CTRL_LPDDR23, DDRMON_CTRL_DDR_TYPE_MASK),
 			       dfi_regs + DDRMON_CTRL);
-	else if (dfi->ddr_type == ROCKCHIP_DDRTYPE_LPDDR4)
+		break;
+	case ROCKCHIP_DDRTYPE_LPDDR4:
 		writel_relaxed(HIWORD_UPDATE(DDRMON_CTRL_LPDDR4, DDRMON_CTRL_DDR_TYPE_MASK),
 			       dfi_regs + DDRMON_CTRL);
+		break;
+	default:
+		break;
+	}
 
 	/* enable count, use software mode */
 	writel_relaxed(HIWORD_UPDATE(DDRMON_CTRL_SOFTWARE_EN, DDRMON_CTRL_SOFTWARE_EN),