xilinx: versal: Setup 30MHz as default spi frequency

Align default SPI configuration with ZynqMP/Versal NET.
There is no reason to run on lower frequencies.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/c1d6ebd659f3002649b1200c926f8b9ed3132085.1698749448.git.michal.simek@amd.com
diff --git a/configs/xilinx_versal_virt_defconfig b/configs/xilinx_versal_virt_defconfig
index b588887..6a2c03c 100644
--- a/configs/xilinx_versal_virt_defconfig
+++ b/configs/xilinx_versal_virt_defconfig
@@ -6,6 +6,7 @@
 CONFIG_TEXT_BASE=0x8000000
 CONFIG_SYS_MALLOC_F_LEN=0x100000
 CONFIG_NR_DRAM_BANKS=36
+CONFIG_SF_DEFAULT_SPEED=30000000
 CONFIG_DEFAULT_DEVICE_TREE="xilinx-versal-virt"
 CONFIG_OF_LIBFDT_OVERLAY=y
 CONFIG_DM_RESET=y