Merge branch 'bugfix/fix_calculation_overflow_of_timer_less_than_0x35A_us_error' into 'release/v2.x.x'

bugfix(hw_timer): fix calculation overflow of timer less than 0x35A us error

See merge request sdk/ESP8266_RTOS_SDK!533

Author: wujiangang

driver_lib/driver/hw_timer.c

@@ -28,7 +28,7 @@
     ((t) ?          \
      (((t) > 0x35A) ?            \
       (((t) >> 2) * ((APB_CLK_FREQ >> 4) / 250000) + ((t)&0x3) * ((APB_CLK_FREQ >> 4) / 1000000)) : \
-      (((t) *(APB_CLK_FREQ>>4)) / 1000000)) :    \
+      ((t) *((APB_CLK_FREQ>>4) / 1000000))) :    \
          0)
 
 #define FRC1_ENABLE_TIMER   BIT7