proc: switch /proc/version to seq_file

and move it to fs/proc/version.c while I'm at it.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
diff --git a/fs/proc/Makefile b/fs/proc/Makefile
index 70607a0..97985c8 100644
--- a/fs/proc/Makefile
+++ b/fs/proc/Makefile
@@ -12,6 +12,7 @@
 proc-y	+= loadavg.o
 proc-y	+= meminfo.o
 proc-y	+= uptime.o
+proc-y	+= version.o
 proc-$(CONFIG_PROC_SYSCTL)	+= proc_sysctl.o
 proc-$(CONFIG_NET)		+= proc_net.o
 proc-$(CONFIG_PROC_KCORE)	+= kcore.o