serial: drop useless ctlr field

The multi serial support has a "ctlr" field which almost no one uses,
but everyone is forced to set to useless strings.  So punt it.

Funny enough, the only code that actually reads this field (the mpc8xx
driver) has a typo where it meant to look for the SCC driver.  Fix it
while converting the check to use the name field.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
CC: Heiko Schocher <hs@denx.de>
CC: Anatolij Gustschin <agust@denx.de>
CC: Tom Rix <Tom.Rix@windriver.com>
CC: Minkyu Kang <mk7.kang@samsung.com>
CC: Craig Nauman <cnauman@diagraph.com>
CC: Marek Vasut <marek.vasut@gmail.com>
CC: Prafulla Wadaskar <prafulla@marvell.com>
CC: Mahavir Jain <mjain@marvell.com>