mtd: lpc32xx_slc: Cleanup after DT-only conversion

mtd: lpc32xx_slc: Cleanup after DT-only conversion

The LPC32xx's DT-only conversion of the SLC NAND driver makes NAND config via
platform_data obsolete. Dropped by this patch.

Further, the driver really needs CONFIG_OF, which is already reflected by the
dependency on ARCH_LPC32XX which depends on CONFIG_OF. So also dropping
CONFIG_OF ifdefs.

There is still platform_data necessary to supply the dma_filter callback for
the dma engine. This is a completely different data structure than the old
platform_data for NAND config, so renaming some old "pdata" variable to "ncfg"
to prevent confusion with the new platform data.

Signed-off-by: Roland Stigge <stigge@antcom.de>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>