init/main.c: log init process file name

Add a log message to `run_init_process()`.

This log message serves two purposes.

1.  If the init process is not specified on the Linux Kernel command
    line, the user sees, what file was chosen.

2.  The time stamps shows exactly, when the Linux kernel handed over
    control to the init process.

Link: http://lkml.kernel.org/r/b1fc97fa-4aa9-1904-ddb5-859e78995c41@molgen.mpg.de


Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>