MIPS: disable CONFIG_IDE in bigsur_defconfig

bigsur_defconfig enables CONFIG_IDE for the tc86c001 ide driver, which
is a Toshiba plug in card that does not make much sense to use on bigsur
platforms.  For all other ATA cards libata support is already enabled.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>