MAINTAINERS: update ST's Mailing list for SPEAr

We have created a ST's Mailing list for SPEAr.  This can be accessed
from non-st email ids.  I want people to cc this list, when they have
changes specific to SPEAr.  So, its better to get this updated in
MAINTAINERS file.

linux-arm-kernel@lists.infradead.org is also added for SPEAr.

Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>