mailmap: Update email for Paul Burton

Paul had left MIPS a couple of years ago, his email address is
no longer valid.

Replace it with his kenrel.org email, which has been used in
kernel and QEMU, in case we still want to reach him.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>

.mailmap

@@ -87,7 +87,8 @@ This contributor prefers not to receive mails <noreply@example.com> <pali@kernel
 This contributor prefers not to receive mails <noreply@example.com> <pali.rohar@gmail.com>
 Patrice Chotard <patrice.chotard@foss.st.com> <patrice.chotard@st.com>
 Patrick Delaunay <patrick.delaunay@foss.st.com> <patrick.delaunay@st.com>
-Paul Burton <paul.burton@mips.com> <paul.burton@imgtec.com>
+Paul Burton <paulburton@kernel.org> <paul.burton@imgtec.com>
+Paul Burton <paulburton@kernel.org> <paul.burton@mips.com>
 Piyush Mehta <piyush.mehta@amd.com> <piyush.mehta@xilinx.com>
 Prabhakar Kushwaha <prabhakar@freescale.com>
 Punnaiah Choudary Kalluri <punnaiah.choudary.kalluri@amd.com> <punnaiah.choudary.kalluri@xilinx.com>

board/imgtec/boston/MAINTAINERS

@@ -1,5 +1,5 @@
 BOSTON BOARD
-M:	Paul Burton <paul.burton@mips.com>
+M:	Paul Burton <paulburton@kernel.org>
 S:	Maintained
 F:  arch/mips/dts/boston-u-boot.dtsi
 F:	board/imgtec/boston/

board/imgtec/malta/MAINTAINERS

@@ -1,5 +1,5 @@
 MALTA BOARD
-M:	Paul Burton <paul.burton@mips.com>
+M:	Paul Burton <paulburton@kernel.org>
 S:	Maintained
 F:	board/imgtec/malta/
 F:	include/configs/malta.h