.mailmap: fix old email addresses

Update Nick & Nadia's old addresses.

Link: https://lkml.kernel.org/r/20210406134036.GQ2531743@casper.infradead.org


Signed-off-by: Matthew Wilcox <willy@infradead.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Nadia Yvette Chambers <nyc@holomorphy.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>