ubi: help message correction

Fix incorrect information about size units and correct typo.
Signed-off-by: NAndrzej Wolski <awolski@poczta.fm>
Signed-off-by: NStefan Roese <sr@denx.de>

common/cmd_ubi.c

@@ -618,7 +618,7 @@ U_BOOT_CMD(ubi, 6, 1, do_ubi,
 	"ubi remove[vol] volume"
 		" - Remove volume\n"
 	"[Legends]\n"
-	" volume: charater name\n"
-	" size: KiB, MiB, GiB, and bytes\n"
+	" volume: character name\n"
+	" size: specified in bytes\n"
 	" type: s[tatic] or d[ynamic] (default=dynamic)"
 );