[ARM] Comment out missing configuration symbols

HAS_TOUCHSCREEN_ADS7843_LH7 and HAS_TOUCHSCREEN_ADC_LH7 are referenced
but not defined in the LH7A40x configuration.  Comment them out to
prevent them causing warnings.

Marc Singer said:

   Feel free to remove the Kconfig lines.  I'll add it back with
   the rest of the config entries.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>