microblaze: fix build failure due to undefined reference to `get_ticks'

after commit "common: add possibility for readline_into_buffer
timeout" (sha1:9c34831) was applied. The Microblaze generic build
fails with error below:

common/libcommon.o: In function `cread_line':
/devel/u-boot/common/main.c:717: undefined reference to `get_ticks'
/devel/u-boot/common/main.c:717: undefined reference to `get_tbclk'
/devel/u-boot/common/main.c:720: undefined reference to `get_ticks'

Signed-off-by: Stephan Linz <linz@li-pro.net>
Acked-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/cpu/timer.c

@@ -62,3 +62,21 @@ int timer_init (void)
 }
 #endif
 #endif
+
+/*
+ * This function is derived from PowerPC code (read timebase as long long).
+ * On Microblaze it just returns the timer value.
+ */
+unsigned long long get_ticks(void)
+{
+	return get_timer(0);
+}
+
+/*
+ * This function is derived from PowerPC code (timebase clock frequency).
+ * On Microblaze it returns the number of timer ticks per second.
+ */
+ulong get_tbclk(void)
+{
+	return CONFIG_SYS_HZ;
+}