Fix various typos, scattered over the code.

Spelling corrections for (among other things):

* environment
* override
* variable
* ftd (should be "fdt", for flattened device tree)
* embedded
* FTDI
* emulation
* controller
diff --git a/board/freescale/common/fsl_validate.c b/board/freescale/common/fsl_validate.c
index 64e4e30..8c171b1 100644
--- a/board/freescale/common/fsl_validate.c
+++ b/board/freescale/common/fsl_validate.c
@@ -812,9 +812,9 @@
 }
 /* haddr - Address of the header of image to be validated.
  * arg_hash_str - Option hash string. If provided, this
- * overides the key hash in the SFP fuses.
+ * overrides the key hash in the SFP fuses.
  * img_addr_ptr - Optional pointer to address of image to be validated.
- * If non zero addr, this overides the addr of image in header,
+ * If non zero addr, this overrides the addr of image in header,
  * otherwise updated to image addr in header.
  * Acts as both input and output of function.
  * This pointer shouldn't be NULL.
diff --git a/board/freescale/mx28evk/README b/board/freescale/mx28evk/README
index a248fb2..b8bee89 100644
--- a/board/freescale/mx28evk/README
+++ b/board/freescale/mx28evk/README
@@ -45,7 +45,7 @@
 
 or
 
-"make mx28evk_spi_config"       - store enviroment variables into SPI NOR flash
+"make mx28evk_spi_config"       - store environment variables into SPI NOR flash
 
 Choose the target accordingly.