spi: aspeed: Fix typo in mode_bits field for AST2600 platform

Both quad SPI TX and RX modes can be supported on AST2600.
Correct typo in mode_bits field in both ast2600_fmc_data
and ast2600_spi_data structs.

Signed-off-by: Chin-Ting Kuo <chin-ting_kuo@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Link: https://lore.kernel.org/r/20221005083209.222272-1-chin-ting_kuo@aspeedtech.com
Signed-off-by: Mark Brown <broonie@kernel.org>