trace: undefined reference to `trace_early_init'

Compiling with TRACE but without TRACE_EARLY results in an error
aarch64-linux-gnu-ld.bfd:
common/built-in.o:(.rodata.init_sequence_f+0x10):
undefined reference to `trace_early_init'

trace_early_init() should not be called if CONFIG_TRACE_EARLY is not
defined.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>