doc: Add more comments for this dma spiflash example

fanghuaqi · fanghuaqi · commit 15c4461afa61 · 2017-03-21T15:51:03.000+08:00
diff --git a/example/baremetal/dma_spiflash/main.c b/example/baremetal/dma_spiflash/main.c
@@ -54,7 +54,8 @@
  *
  * ### Extra Comments
  *    Tested in EMSK 2.3 EM9D, for drivers with DMA, spiflash working frequency can achieve 12Mhz.
- *    For drivers without DMA, spiflash working frequency can achieve 12Mhz.
+ *    For drivers without DMA, spiflash working frequency can achieve 2Mhz.
+ *    This example will stuck at the max frequency that SPI can achieve at that situation.
  */
 
 /**

Original file line number	Diff line number	Diff line change
`@@ -54,7 +54,8 @@`
`54`	`54`	`*`
`55`	`55`	`* ### Extra Comments`
`56`	`56`	`* Tested in EMSK 2.3 EM9D, for drivers with DMA, spiflash working frequency can achieve 12Mhz.`
`57`		`- * For drivers without DMA, spiflash working frequency can achieve 12Mhz.`
	`57`	`+ * For drivers without DMA, spiflash working frequency can achieve 2Mhz.`
	`58`	`+ * This example will stuck at the max frequency that SPI can achieve at that situation.`
`58`	`59`	`*/`
`59`	`60`
`60`	`61`	`/**`