toolchain/buildroot: default to eglibc for mips64

uClibc only works well for O32 ABI on mips64, so default to eglibc that
works just fine with N32 & N64 ABIs as well.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

toolchain/toolchain-buildroot/Config.in

@@ -5,6 +5,7 @@ source "package/linux-headers/Config.in.host"
 
 choice
 	prompt "C library"
+	default BR2_TOOLCHAIN_BUILDROOT_EGLIBC if BR2_mips64 || BR2_mips64el
 
 config BR2_TOOLCHAIN_BUILDROOT_UCLIBC
 	bool "uClibc"