ARM: OMAP2+: Fix error handling for omap2_clk_enable_init_clocks

We need to check if we got the clock before trying to do anything
with it. Otherwise we will get something like this:

Unable to handle kernel paging request at virtual address fffffffe
...
[<c04bef78>] (clk_prepare) from [<c00338a4>] (omap2_clk_enable_init_clocks+0x50/0x8)
[<c00338a4>] (omap2_clk_enable_init_clocks) from [<c0876838>] (dm816x_dt_clk_init+0)
...

Let's add check for the clock and WARN if the init clock was not
found.

Cc: Brian Hutchinson <b.hutchman@gmail.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Tero Kristo <t-kristo@ti.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/clock.c

@@ -620,6 +620,9 @@ void omap2_clk_enable_init_clocks(const char **clk_names, u8 num_clocks)
 
 	for (i = 0; i < num_clocks; i++) {
 		init_clk = clk_get(NULL, clk_names[i]);
+		if (WARN(IS_ERR(init_clk), "could not find init clock %s\n",
+				clk_names[i]))
+			continue;
 		clk_prepare_enable(init_clk);
 	}
 }