pico-pi-imx7d: Unselect CONFIG_CONSOLE_MUX

Unselect CONFIG_CONSOLE_MUX to fix the following
error for the input, output and error interfaces:

U-Boot 2023.10 (Oct 03 2023 - 21:23:18 -0300)
...
In:    No input devices available!
Out:   No output devices available!
Err:   No error devices available!
Net:   eth0: ethernet@30be0000
Hit any key to stop autoboot:  0

Signed-off-by: Fabio Estevam <festevam@denx.de>
diff --git a/configs/pico-imx7d_bl33_defconfig b/configs/pico-imx7d_bl33_defconfig
index 289cf6b..18fb5d2 100644
--- a/configs/pico-imx7d_bl33_defconfig
+++ b/configs/pico-imx7d_bl33_defconfig
@@ -24,6 +24,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_USE_BOOTCOMMAND=y
 CONFIG_BOOTCOMMAND="run distro_bootcmd"
+# CONFIG_CONSOLE_MUX is not set
 CONFIG_SPL_MAX_SIZE=0xe000
 CONFIG_SPL_HAS_BSS_LINKER_SECTION=y
 CONFIG_SPL_BSS_MAX_SIZE=0x100000