Merge pull request #5248 from mysterywolf/delayus

[bsp] remove empty rt_hw_us_delay

bsp/bluetrum/ab32vg1-ab-prougen/board/board.c

@@ -145,11 +145,6 @@ void rt_hw_board_init(void)
 #endif
 }
 
-void rt_hw_us_delay(rt_uint32_t us)
-{
-
-}
-
 RT_SECTION(".irq.cache")
 void cache_init(void)
 {

bsp/mini2440/drivers/board.c

@@ -122,9 +122,4 @@ void rt_hw_board_init(void)
 
 }
 
-void rt_hw_us_delay(rt_uint32_t us)
-{
-
-}
-
 /*@}*/

bsp/qemu-vexpress-a9/drivers/board.c

@@ -56,7 +56,3 @@ void rt_hw_board_init(void)
 #endif
 }
 
-void rt_hw_us_delay(rt_uint32_t us)
-{
-
-}