char: remove the SGI snsc driver

The SGI SN2 support is about to be removed.  Remove this driver that
depends on the SN2 support.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lkml.kernel.org/r/20190813072514.23299-2-hch@lst.de
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/configs/generic_defconfig

@@ -90,7 +90,6 @@ CONFIG_IGB=y
 # CONFIG_SERIO_SERPORT is not set
 CONFIG_GAMEPORT=m
 CONFIG_SERIAL_NONSTANDARD=y
-CONFIG_SGI_SNSC=y
 CONFIG_SGI_TIOCX=y
 CONFIG_SGI_MBCS=m
 CONFIG_SERIAL_8250=y

arch/ia64/configs/gensparse_defconfig

@@ -79,7 +79,6 @@ CONFIG_E1000=y
 # CONFIG_SERIO_SERPORT is not set
 CONFIG_GAMEPORT=m
 CONFIG_SERIAL_NONSTANDARD=y
-CONFIG_SGI_SNSC=y
 CONFIG_SGI_TIOCX=y
 CONFIG_SGI_MBCS=m
 CONFIG_SERIAL_8250=y