fix: 'sp_mk_generator.py' reference to undef var

The script 'sp_mk_generator.py' was reworked in [1]. There was a
reference the variable 'data' left. This variable 'data' used to refer
to the json data of a the sp layout file.
This patch fixed the reference with the proper variable according to the
rework [1].

[1] https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git/commit/?id=a96a07bfb66b7d38fe3da824e8ba183967659008

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: I9ddbfa8d55a114bcef6997920522571e070fc7d2

tools/sptool/sp_mk_generator.py

@@ -196,7 +196,7 @@ def gen_fiptool_args(sp_layout, sp, args :dict):
     ''' Generate arguments for the FIP Tool. '''
     if "uuid" in sp_layout[sp]:
         # Extract the UUID from the JSON file if the SP entry has a 'uuid' field
-        uuid_std = uuid.UUID(data[key]['uuid'])
+        uuid_std = uuid.UUID(sp_layout[sp]['uuid'])
     else:
         with open(get_sp_manifest_full_path(sp_layout[sp], args), "r") as pm_f:
             uuid_lines = [l for l in pm_f if 'uuid' in l]