drivers/char/random.c: constify poolinfo_table

commit 26e0854ab3310bbeef1ed404a2c87132fc91f8e1 upstream.

Never modified, might as well be put in .rodata.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>