Cosmetic: Fix a number of typos, no functional changes.

Fix various misspellings of things like "environment", "kernel",
"default" and "volatile", and throw in a couple grammar fixes.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
diff --git a/board/freescale/mx28evk/README b/board/freescale/mx28evk/README
index 524f3fc..0389a1d 100644
--- a/board/freescale/mx28evk/README
+++ b/board/freescale/mx28evk/README
@@ -29,11 +29,11 @@
 
 There are two targets for mx28evk:
 
-"make mx28evk_config"		- store enviroment variables into MMC
+"make mx28evk_config"		- store environment variables into MMC
 
 or
 
-"make mx28evk_nand_config"	- store enviroment variables into NAND flash
+"make mx28evk_nand_config"	- store environment variables into NAND flash
 
 Choose the target accordingly.