am335x, guardian: fix spl usb-eth boot

- On Guardian board, usb-eth boot in SPL stage fails due to certain
   misconfiguration. Hence, add the same to fix the issue.

 - configs are set based on the conditional statement present in
   arch/arm/mach-omap2/am33xx/board.c

 - disable tiny printf in SPL stage:
    As the library is optimized, the ability to deal with ethaddr is lost.
    The following message would be printed on the console,

    Error: flags type check failure for "ethaddr" <= "80a81144M" (type: m)
    Error inserting "ethaddr" variable, errno=1

Signed-off-by: Moses Christopher <BollavarapuMoses.Christopher@in.bosch.com>
diff --git a/configs/am335x_guardian_defconfig b/configs/am335x_guardian_defconfig
index 13974f7..eb2d221 100644
--- a/configs/am335x_guardian_defconfig
+++ b/configs/am335x_guardian_defconfig
@@ -52,7 +52,7 @@
 # CONFIG_ISO_PARTITION is not set
 # CONFIG_SPL_EFI_PARTITION is not set
 CONFIG_OF_CONTROL=y
-CONFIG_SPL_OF_CONTROL=y
+# CONFIG_SPL_OF_CONTROL is not set
 CONFIG_DEFAULT_DEVICE_TREE="am335x-guardian"
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_SPL_DM=y
@@ -87,3 +87,5 @@
 CONFIG_USB_ETHER=y
 CONFIG_SPL_WDT=y
 CONFIG_FAT_WRITE=y
+CONFIG_SPL_OF_LIBFDT=y
+# CONFIG_SPL_USE_TINY_PRINTF is not set