MIPS: Lasat: Add missing CONFIG_PROC_FS dependency to PICVUE_PROC

MIPS: Lasat: Add missing CONFIG_PROC_FS dependency to PICVUE_PROC

The picvue_proc.c file creates the /proc interface for the PICVUE LCD
display driver. As a result of which, it needs to depend on the PROC_FS
symbol to avoid build problems like the following one when
CONFIG_PROC_FS is not enabled.

arch/mips/lasat/picvue_proc.c:26:14: error: 'pvc_linename'
defined but not used [-Werror=unused-variable]
 static char *pvc_linename[PVC_NLINES] = {"line1", "line2"};
              ^

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8174/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>