arch, board: squash lines for immediate return

Remove unneeded variables and assignments.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Minkyu Kang <mk7.kang@samsung.com>
Reviewed-by: Angelo Dureghello <angelo@sysam.it>
diff --git a/arch/m68k/lib/time.c b/arch/m68k/lib/time.c
index 3163354..cb90c83 100644
--- a/arch/m68k/lib/time.c
+++ b/arch/m68k/lib/time.c
@@ -192,7 +192,5 @@
  */
 ulong get_tbclk(void)
 {
-	ulong tbclk;
-	tbclk = CONFIG_SYS_HZ;
-	return tbclk;
+	return CONFIG_SYS_HZ;
 }