mtd: chips: reorganize Kconfig help on swapping

The Kconfig help on "Flash cmd/query data swapping" still mentions
LART_ENDIAN_BYTE. That option used to be relevant for setting
CONFIG_MTD_CFI_LART_BIT_SWAP. That option and macro got both removed in
v2.4.11-pre4. So, although LART endianness sounds intriguing, that part
of the help text can be removed.

And, while we're touching this choice, move the help text up one level.
Currently it's available under the "NO" option, while it's relevant for
all three options.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>