arch: enable private libgcc for m68k

This patch fixes u-boot hanging on the first printf("%x", val).

Some toolchains built without multilib enabled may produce
u-boot freezing on first u64 shift operation, as in
lib/vsprintf.c number() function.
Using our private libgcc solves the issue.

Setting private libgcc enabled at architecture level to avoid
similar issues, it should not harm.

Signed-off-by: Angelo Durgehello <angelo@kernel-space.org>
diff --git a/arch/Kconfig b/arch/Kconfig
index d30676a..55b9a5e 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -67,6 +67,7 @@
 config M68K
 	bool "M68000 architecture"
 	select HAVE_PRIVATE_LIBGCC
+	select USE_PRIVATE_LIBGCC
 	select NEEDS_MANUAL_RELOC
 	select SYS_BOOT_GET_CMDLINE
 	select SYS_BOOT_GET_KBD