sunxi: Kconfig: use SoC-wide values for some symbols

Some configuration symbols formerly defined in header files were
recently converted to Kconfig symbols. This moved their value definition
into *every* defconfig file, even though those values are hardly board
choices.
Use the new Kconfig option to define per-SoC default values, in just one
place, which makes the definition in each defconfig file redundant.

We refrain from setting a sunxi specific value for CONFIG_SYS_BOOTM_LEN,
so this defaults to a much better 64MB for uncompressed arm64 kernels.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/cmd/Kconfig b/cmd/Kconfig
index 49247a4..16030e3 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -86,6 +86,7 @@
 
 config SYS_PBSIZE
 	int "Buffer size for console output"
+	default 1024 if ARCH_SUNXI
 	default 1044
 
 config SYS_XTRACE