checkpatch: define typedefsfile to deal with a few false positives

checkpatch expects typedefs to be suffixed with _t and has different
rules when typedefs are being used as arguments of a function. This
seems to be a known issue and defining typedefs in a file resolves this
issue.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

.checkpatch.conf

@@ -5,6 +5,7 @@
 --show-types
 --max-line-length=80
 --min-conf-desc-length=1
+--typedefsfile=scripts/checkpatch/typedefsfile
 
 --ignore BRACES
 --ignore PRINTK_WITHOUT_KERN_LEVEL

scripts/checkpatch/typedefsfile

@@ -0,0 +1 @@
+mbedtls_pk_context