cmd_fat.c: fix build warning

Commit cfda5aeab89d73779e26f0d34cf10f64caa67431
(cmd_fat: use common get_device_and_partition function)
introduced a warning:
cmd_fat.c: In function 'do_fat_fswrite':
cmd_fat.c:178:8: warning: unused variable 'ep' [-Wunused-variable]

Fix it.

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Reported-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
Tested-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
diff --git a/common/cmd_fat.c b/common/cmd_fat.c
index 55585c6..5a5698b 100644
--- a/common/cmd_fat.c
+++ b/common/cmd_fat.c
@@ -175,7 +175,6 @@
 	disk_partition_t info;
 	int dev = 0;
 	int part = 1;
-	char *ep;
 
 	if (argc < 5)
 		return cmd_usage(cmdtp);