trace: conserve gd register on RISC-V

An UEFI application may change the value of the register that gd lives in.
But some of our functions like get_ticks() access this register. So we
have to set the gd register to the U-Boot value when entering a trace
point and set it back to the application value when exiting the trace
point.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/lib/trace.c b/lib/trace.c
index 831283c..defc971 100644
--- a/lib/trace.c
+++ b/lib/trace.c
@@ -57,7 +57,7 @@
 	return offset / FUNC_SITE_SIZE;
 }
 
-#if defined(CONFIG_EFI_LOADER) && defined(CONFIG_ARM)
+#if defined(CONFIG_EFI_LOADER) && (defined(CONFIG_ARM) || defined(CONFIG_RISCV))
 
 /**
  * trace_gd - the value of the gd register