doc: fix misspellings

Signed-off-by: Guilherme Maciel Ferreira <guilherme.maciel.ferreira@gmail.com>

doc/uImage.FIT/source_file_format.txt

@@ -159,7 +159,7 @@ the '/images' node should have the following layout:
   - description : Textual description of the component sub-image
   - type : Name of component sub-image type, supported types are:
     "standalone", "kernel", "ramdisk", "firmware", "script", "filesystem",
-    "flat_dt" and others (see uimage_type in common/images.c).
+    "flat_dt" and others (see uimage_type in common/image.c).
   - data : Path to the external file which contains this node's binary data.
   - compression : Compression used by included data. Supported compressions
     are "gzip" and "bzip2". If no compression is used compression property

doc/uImage.FIT/verified-boot.txt

@@ -64,7 +64,7 @@ software from updatable memory.
 
 It is critical that the public key be secure and cannot be tampered with.
 It can be stored in read-only memory, or perhaps protected by other on-chip
-crypto provided by some modern SOCs. If the public key can ben changed, then
+crypto provided by some modern SOCs. If the public key can be changed, then
 the verification is worthless.
 
 
@@ -87,7 +87,7 @@ affect the whole change.
 
 Flattened Image Tree (FIT)
 --------------------------
-The FIT format is alreay widely used in U-Boot. It is a flattened device
+The FIT format is already widely used in U-Boot. It is a flattened device
 tree (FDT) in a particular format, with images contained within. FITs
 include hashes to verify images, so it is relatively straightforward to
 add signatures as well.