i2c: designware: make const array supported_speeds static to shink object code size

Don't populate const array supported_speeds on the stack, instead
make it static.  Makes the object code smaller by 150 bytes:

Before:
   text	   data	    bss	    dec	    hex	filename
   8474	   1440	      0	   9914	   26ba	i2c-designware-platdrv.o

After:
   text	   data	    bss	    dec	    hex	filename
   8324	   1440	      0	   9764	   2624	i2c-designware-platdrv.o

(gcc version 7.2.0 x86_64)
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Acked-by: NJarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-designware-platdrv.c

@@ -265,7 +265,9 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
 	u32 acpi_speed, ht = 0;
 	struct resource *mem;
 	int i, irq, ret;
-	const int supported_speeds[] = { 0, 100000, 400000, 1000000, 3400000 };
+	static const int supported_speeds[] = {
+		0, 100000, 400000, 1000000, 3400000
+	};
 
 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0)