oem: meta: Add decode_oem_meta_file_io_req()

Support decode_oem_meta_file_io_req() cmd to decode the incoming post
code.

PLDM OEM Meta Write File IO cmd:
Example:
  Request:
    Byte 0: 0x3F (OEM cmd)
    Byte 1: 0x02 (FILE IO)
    Byte 2: 0x00 (File io type : POST CODE)
    Byte 3-6: 0x04 (Data length)
    Byte 7-10: 0x93 0xE0 0x00 0xEA (post code)

  Response:
    Byte 0: 0x00 (success)

Tested:
- Unit Tests passed.

Change-Id: I85437698642dd3cbe6084acf1feada842d206eac
Signed-off-by: Delphine CC Chiu <Delphine_CC_Chiu@wiwynn.com>
diff --git a/tests/meson.build b/tests/meson.build
index 76ca6ee..dba7870 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -45,6 +45,12 @@
   ]
 endif
 
+if get_option('oem-meta').allowed()
+  tests += [
+    'oem/meta/libpldm_fileio_test',
+  ]
+endif
+
 test_include_dirs = [ libpldm_include_dir, include_directories('../src') ]
 
 foreach t : tests