scripts/spdxcheck.py: make python3 compliant

Without this change the following happens when using Python3 (3.6.6):

	$ echo "GPL-2.0" | python3 scripts/spdxcheck.py -
	FAIL: 'str' object has no attribute 'decode'
	Traceback (most recent call last):
	  File "scripts/spdxcheck.py", line 253, in <module>
	    parser.parse_lines(sys.stdin, args.maxlines, '-')
	  File "scripts/spdxcheck.py", line 171, in parse_lines
	    line = line.decode(locale.getpreferredencoding(False), errors='ignore')
	AttributeError: 'str' object has no attribute 'decode'

So as the line is already a string, there is no need to decode it and
the line can be dropped.

/usr/bin/python on Arch is Python 3.  So this would indeed be worth
going into 4.19.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Uwe Kleine-König <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Joe Perches <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

scripts/spdxcheck.py

@@ -168,7 +168,6 @@ class id_parser(object):
         self.curline = 0
         try:
             for line in fd:
-                line = line.decode(locale.getpreferredencoding(False), errors='ignore')
                 self.curline += 1
                 if self.curline > maxlines:
                     break