clk: visconti: prevent array overflow in visconti_clk_register_gates()

This code was using -1 to represent that there was no reset function.
Unfortunately, the -1 was stored in u8 so the if (clks[i].rs_id >= 0)
condition was always true.  This lead to an out of bounds access in
visconti_clk_register_gates().

Fixes: b4cbe60 ("clk: visconti: Add support common clock driver and reset driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20220316083533.GA30941@kili
Acked-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

Author: Dan Carpenter

drivers/clk/visconti/clkc-tmpv770x.c

@@ -176,7 +176,7 @@ static const struct visconti_clk_gate_table clk_gate_tables[] = {
 	{ TMPV770X_CLK_WRCK, "wrck",
 		clks_parent_data, ARRAY_SIZE(clks_parent_data),
 		0, 0x68, 0x168, 9, 32,
-		-1, }, /* No reset */
+		NO_RESET, },
 	{ TMPV770X_CLK_PICKMON, "pickmon",
 		clks_parent_data, ARRAY_SIZE(clks_parent_data),
 		0, 0x10, 0x110, 8, 4,

drivers/clk/visconti/clkc.c

@@ -147,7 +147,7 @@ int visconti_clk_register_gates(struct visconti_clk_provider *ctx,
 		if (!dev_name)
 			return -ENOMEM;
 
-		if (clks[i].rs_id >= 0) {
+		if (clks[i].rs_id != NO_RESET) {
 			rson_offset = reset[clks[i].rs_id].rson_offset;
 			rsoff_offset = reset[clks[i].rs_id].rsoff_offset;
 			rs_idx = reset[clks[i].rs_id].rs_idx;

drivers/clk/visconti/clkc.h

@@ -73,4 +73,7 @@ int visconti_clk_register_gates(struct visconti_clk_provider *data,
 				 int num_gate,
 				 const struct visconti_reset_data *reset,
 				 spinlock_t *lock);
+
+#define NO_RESET 0xFF
+
 #endif /* _VISCONTI_CLKC_H_ */