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/arch/mips/Kconfig b/arch/mips/Kconfig
index f852a1f..fe37d1f 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -145,7 +145,7 @@
 	  Enable this option if you want U-Boot to hand over the Yamon-style
 	  environment to the kernel. Information like memory size, initrd
 	  address and size will be prepared as zero-terminated key/value list.
-	  The address of the enviroment is stored in register $a2.
+	  The address of the environment is stored in register $a2.
 
 config MIPS_BOOT_FDT
 	bool "Hand over a flattened device tree to Linux kernel"