MAINTAINERS: POWERPC MPC8XX: Update email address

Our email addresses have changed from @c-s.fr to @csgroup.eu

Update entry in MAINTAINERS
Signed-off-by: NChristophe Leroy <christophe.leroy@csgroup.eu>

MAINTAINERS

@@ -818,7 +818,7 @@ S:	Maintained
 F:	arch/powerpc/
 
 POWERPC MPC8XX
-M:	Christophe Leroy <christophe.leroy@c-s.fr>
+M:	Christophe Leroy <christophe.leroy@csgroup.eu>
 S:	Maintained
 T:	git https://gitlab.denx.de/u-boot/custodians/u-boot-mpc8xx.git
 F:	arch/powerpc/cpu/mpc8xx/