.mailmap: Update Paul Burton email address

Following the Linux kernel equivalent patch posted on
linux-mips@vger.kernel.org [*], update Paul Burton email
address to avoid emails bouncing.

[*] 'MAINTAINERS: Use @kernel.org address for Paul Burton'
https://lore.kernel.org/patchwork/patch/1140341/

Cc: Paul Burton <paulburton@kernel.org>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Acked-by: Paul Burton <paulburton@kernel.org>
Message-Id: <20200707022544.24925-1-f4bug@amsat.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

.mailmap

@@ -51,9 +51,10 @@ Frederic Konrad <konrad@adacore.com> <fred.konrad@greensocs.com>
 James Hogan <jhogan@kernel.org> <james.hogan@imgtec.com>
 Leif Lindholm <leif@nuviainc.com> <leif.lindholm@linaro.org>
 Radoslaw Biernacki <rad@semihalf.com> <radoslaw.biernacki@linaro.org>
-Paul Burton <pburton@wavecomp.com> <paul.burton@mips.com>
-Paul Burton <pburton@wavecomp.com> <paul.burton@imgtec.com>
-Paul Burton <pburton@wavecomp.com> <paul@archlinuxmips.org>
+Paul Burton <paulburton@kernel.org> <paul.burton@mips.com>
+Paul Burton <paulburton@kernel.org> <paul.burton@imgtec.com>
+Paul Burton <paulburton@kernel.org> <paul@archlinuxmips.org>
+Paul Burton <paulburton@kernel.org> <pburton@wavecomp.com>
 Stefan Brankovic <stefan.brankovic@syrmia.com> <stefan.brankovic@rt-rk.com.com>
 Yongbok Kim <yongbok.kim@mips.com> <yongbok.kim@imgtec.com>