clk: scpi: bound-check DVFS index in scpi_dvfs_recalc_rate

dvfs_get_idx() may return an out-of-range index if the SCP firmware is
buggy or returns a stale value. Only negative indexes were rejected, so a
large index walked past info->opps and could treat garbage as a clock rate
(KASAN OOB / wrong frequency to consumers). The missing upper bound dates
back to the original SCPI clock driver.

Treat indexes >= opp count as invalid and return 0, same as idx < 0.

Fixes: cd52c2a4b5 ("clk: add support for clocks provided by SCP(System Control Processor)")
Signed-off-by: Xixin Liu <liuxixin@kylinos.cn>
Link: https://patch.msgid.link/04f9ab766e07.v2.1785200642.git.liuxixin@kylinos.cn
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>

drivers/clk/clk-scpi.c

@@ -73,7 +73,7 @@ static unsigned long scpi_dvfs_recalc_rate(struct clk_hw *hw,
 	int idx = clk->scpi_ops->dvfs_get_idx(clk->id);
 	const struct scpi_opp *opp;
 
-	if (idx < 0)
+	if (idx < 0 || idx >= clk->info->count)
 		return 0;
 
 	opp = clk->info->opps + idx;