trace: Don't require TIMER_EARLY

Some platforms cannot honour this and don't need trace before relocation.
Use 'imply' instead, so boards can disable this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/Kconfig b/lib/Kconfig
index 36d3cf9..2425296 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -316,7 +316,7 @@
 config TRACE
 	bool "Support for tracing of function calls and timing"
 	imply CMD_TRACE
-	select TIMER_EARLY
+	imply TIMER_EARLY
 	help
 	  Enables function tracing within U-Boot. This allows recording of call
 	  traces including timing information. The command can write data to