MAINTAINERS: update phylink/sfp keyword matching

syzbot has revealed that the "phylink" keyword exists in non-phylink
related contexts in the bluetooth stack. To avoid receiving
inappropriate notifications, change the keyword matching regexp to
something which avoids this, while still allowing changes to networking
drivers that make use of phylink to be detected.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>