ARM: omap2: gpmc: Fix gpmc_cs_reserved() return value

Currently gpmc_cs_reserved() return value is somewhat inconsistent,
returning a negative value on an error condition, a positive value
if the chip select is reserved and zero if it's available.

Fix this by returning a boolean value as the function name suggests:
  * true if the chip select is reserved,
  * false if it's available

Suggested-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Reviewed-by: Jon Hunter <jon-hunter@ti.com>
Signed-off-by: Jon Hunter <jon-hunter@ti.com>

arch/arm/mach-omap2/gpmc.c

@@ -452,10 +452,10 @@ static int gpmc_cs_set_reserved(int cs, int reserved)
 	return 0;
 }
 
-static int gpmc_cs_reserved(int cs)
+static bool gpmc_cs_reserved(int cs)
 {
 	if (cs > GPMC_CS_NUM)
-		return -ENODEV;
+		return true;
 
 	return gpmc_cs_map & (1 << cs);
 }