MAINTAINERS: update email for Joel Granados

Change my contact email in MAINTAINERS and .mailmap to my kernel.org.
This in order to avoid cumbersome corporate email policies.
Signed-off-by: Joel Granados <j.granados@samsung.com>

.mailmap

@@ -311,6 +311,7 @@ Jiri Slaby <jirislaby@kernel.org> <xslaby@fi.muni.cz>
 Jisheng Zhang <jszhang@kernel.org> <jszhang@marvell.com>
 Jisheng Zhang <jszhang@kernel.org> <Jisheng.Zhang@synaptics.com>
 Jishnu Prakash <quic_jprakash@quicinc.com> <jprakash@codeaurora.org>
+Joel Granados <joel.granados@kernel.org> <j.granados@samsung.com>
 Johan Hovold <johan@kernel.org> <jhovold@gmail.com>
 Johan Hovold <johan@kernel.org> <johan@hovoldconsulting.com>
 John Crispin <john@phrozen.org> <blogic@openwrt.org>

MAINTAINERS

@@ -18334,7 +18334,7 @@ F:	tools/testing/selftests/proc/
 PROC SYSCTL
 M:	Luis Chamberlain <mcgrof@kernel.org>
 M:	Kees Cook <kees@kernel.org>
-M:	Joel Granados <j.granados@samsung.com>
+M:	Joel Granados <joel.granados@kernel.org>
 L:	linux-kernel@vger.kernel.org
 L:	linux-fsdevel@vger.kernel.org
 S:	Maintained