configs: ls1046aqds: Move CONFIG_SPI_FLASH_* definitions to defconfigs

LS1046A-QDS has CONFIG_SPI_FLASH_SST, CONFIG_SPI_FLASH_EON and
CONFIG_SPI_FLASH_STMICRO defines present in header. Move these entries
from header to defconfigs.

Signed-off-by: Kuldeep Singh <kuldeep.singh@nxp.com>
[Rebased]
Signed-off-by: Priyanka Jain <priyanka.jain@nxp.com>