arch: k210: Add a workaround for clock stabilization

Summary:
- I noticed that sometimes uart shows nothing on the maix-bit board.
- This commit adds a workaround to avoid such the issue

Impact:
- k210 only

Testing:
- Tested with maix-bit

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

arch/risc-v/src/k210/k210_clockconfig.c

@@ -105,5 +105,9 @@ void k210_clockconfig(void)
 
       g_cpu_clock = OSC_FREQ;
     }
+
+  /* Workaround for stabilization */
+
+  up_udelay(1);
 #endif
 }