drivers: wireless: Fix ASSERT() in _read_data_len() in gs2200m.c

Summary:
- During stress test with spresense:wifi (non-SMP), I noticed
  sometimes ASSERT() happened in _read_data_len()
- Actually, up_udelay(50) has been added to avoid the ASSERT
- However, I finally noticed that it should be moved before
  calling dready()
- Also, I cofirmed that we can reduced the time from 50 to 30
- NOTE: we need at least 15us in my experience

Impact:
- gs2200m.c only

Testing:
- Tested with following configurations
- spresense:wifi, spresense:wifi_smp, stm32f4discovery:wifi

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

drivers/wireless/gs2200m.c

@@ -865,6 +865,12 @@ retry:
 
   _write_data(dev, hdr, sizeof(hdr));
 
+  /* NOTE: busy wait 30us
+   * workaround to avoid an invalid frame response
+   */
+
+  up_udelay(30);
+
   /* Wait for data ready */
 
   while (!dev->lower->dready(NULL))
@@ -872,12 +878,6 @@ retry:
       /* TODO: timeout */
     }
 
-  /* NOTE: busy wait 50us
-   * workaround to avoid an invalid frame response
-   */
-
-  up_udelay(50);
-
   /* Read frame response */
 
   _read_data(dev, res, sizeof(res));