mtd: nand: lpc32xx mlc: predefine number of NAND chips to support

mtd: nand: lpc32xx mlc: predefine number of NAND chips to support

Build option CONFIG_SYS_MAX_NAND_CHIPS is used by NXP LPC32xx NAND MLC
driver only, as a preparation for potential removal or replacement of
the option the change predefines CONFIG_SYS_MAX_NAND_CHIPS to 1, same
value is used by the single user Work Microwave Work 92105 board, thus
it will be safe now to remove the option as a board specific one.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>