.mailmap: Add Maciej W. Rozycki's Imagination e-mail address

Following my recent transition from Imagination Technologies to the=20
reincarnated MIPS company add a .mailmap mapping for my work address,
so that `scripts/get_maintainer.pl' gets it right for past commits.

Signed-off-by: Maciej W. Rozycki <macro@mips.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>