sign_encrypt.py: Fix typo from 'Unkown' to 'Unknown'

The value of enc_algo_name and flags_name was set to 'Unkown',
should be 'Unknown' instead.

Signed-off-by: Aristo Chen <aristo.chen@canonical.com>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
diff --git a/scripts/sign_encrypt.py b/scripts/sign_encrypt.py
index ad47a41..1448b6e 100755
--- a/scripts/sign_encrypt.py
+++ b/scripts/sign_encrypt.py
@@ -593,7 +593,7 @@
                  tag_len] = struct.unpack('<IIHH', ehdr)
 
                 print(' struct shdr_encrypted_ta')
-                enc_algo_name = 'Unkown'
+                enc_algo_name = 'Unknown'
                 if enc_algo in enc_tee_alg.values():
                     enc_algo_name = value_to_key(enc_tee_alg, enc_algo)
                 print('  enc_algo:   0x{:08x} ({})'
@@ -603,7 +603,7 @@
                     raise Exception('Unrecognized encrypt algorithm: 0x{:08x}'
                                     .format(enc_algo))
 
-                flags_name = 'Unkown'
+                flags_name = 'Unknown'
                 if flags in enc_key_type.values():
                     flags_name = value_to_key(enc_key_type, flags)
                 print('  flags:      0x{:x} ({})'.format(flags, flags_name))