OMAP3: fix warnings when NAND/ONENAND is not used

Fix build warnings by putting specific used variables
under required #ifdefs for removing:
mem.c:227: warning: unused variable 'f_sec'
mem.c:226: warning: unused variable 'f_off'
mem.c:225: warning: unused variable 'size'
mem.c:224: warning: unused variable 'base'
mem.c:222: warning: unused variable 'gpmc_config'

Signed-off-by: Nishanth Menon <nm@ti.com>

cpu/arm_cortexa8/omap3/mem.c

@@ -218,12 +218,16 @@ void enable_gpmc_cs_config(u32 *gpmc_config, struct gpmc_cs *cs, u32 base,
 void gpmc_init(void)
 {
 	/* putting a blanket check on GPMC based on ZeBu for now */
-	u32 *gpmc_config = NULL;
 	gpmc_cfg = (struct gpmc *)GPMC_BASE;
+#if defined(CONFIG_CMD_NAND) || defined(CONFIG_CMD_ONENAND)
+	u32 *gpmc_config = NULL;
 	u32 base = 0;
 	u32 size = 0;
+#if defined(CONFIG_ENV_IS_IN_NAND) || defined(CONFIG_ENV_IS_IN_ONENAND)
 	u32 f_off = CONFIG_SYS_MONITOR_LEN;
 	u32 f_sec = 0;
+#endif
+#endif
 	u32 config = 0;
 
 	/* global settings */