bus: ti-sysc: Improve reset to work with modules with no sysconfig

At least display susbsystem (DSS) has modules with no sysconfig registers
and rely on custom function for module reset handling. Let's make reset
work with that too.
Signed-off-by: Tony Lindgren <tony@atomide.com>

drivers/bus/ti-sysc.c

@@ -1571,7 +1571,7 @@ static int sysc_reset(struct sysc *ddata)
 	sysc_offset = ddata->offsets[SYSC_SYSCONFIG];
 	syss_offset = ddata->offsets[SYSC_SYSSTATUS];
 
-	if (ddata->legacy_mode || sysc_offset < 0 ||
+	if (ddata->legacy_mode ||
 	    ddata->cap->regbits->srst_shift < 0 ||
 	    ddata->cfg.quirks & SYSC_QUIRK_NO_RESET_ON_INIT)
 		return 0;
@@ -1586,9 +1586,11 @@ static int sysc_reset(struct sysc *ddata)
 	if (ddata->pre_reset_quirk)
 		ddata->pre_reset_quirk(ddata);
 
-	sysc_val = sysc_read_sysconfig(ddata);
-	sysc_val |= sysc_mask;
-	sysc_write(ddata, sysc_offset, sysc_val);
+	if (sysc_offset >= 0) {
+		sysc_val = sysc_read_sysconfig(ddata);
+		sysc_val |= sysc_mask;
+		sysc_write(ddata, sysc_offset, sysc_val);
+	}
 
 	if (ddata->cfg.srst_udelay)
 		usleep_range(ddata->cfg.srst_udelay,