armv8: QSPI: Add AHB bus 16MB+ size support

The default configuration for QSPI AHB bus can't support 16MB+.
But some flash on NXP layerscape board are more than 16MB.

Signed-off-by: Yuan Yao <yao.yuan@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>
diff --git a/configs/ls1046ardb_qspi_defconfig b/configs/ls1046ardb_qspi_defconfig
index 8508c09..fa17373 100644
--- a/configs/ls1046ardb_qspi_defconfig
+++ b/configs/ls1046ardb_qspi_defconfig
@@ -24,3 +24,4 @@
 CONFIG_SYS_NS16550=y
 CONFIG_DM_SPI=y
 CONFIG_FSL_QSPI=y
+CONFIG_QSPI_AHB_INIT=y