tests: fix use of reserved words in test-regselect
tests: fix use of reserved words in test-regselect

"not" is a reserved word, even though gcc may permit it to be used. Avoid
doing so.

Signed-off-by: Nico Reißmann <d8255cca0642bdc1e6f9b45da9cb618d308e389b@gmail.com>

phate/jive,phate/jive,phate/jive