[RANDOM] Move two variables to read_mostly section to save memory

[Eric Dumazet]

While examining vmlinux namelist on i686, I noticed :

c0581300 D random_table
c0581480 d input_pool
c0581580 d random_read_wakeup_thresh
c0581584 d random_write_wakeup_thresh
c0581600 d blocking_pool

That means that the two integers random_read_wakeup_thresh and 
random_write_wakeup_thresh use a full cache entry (128 bytes).

Moving them to read_mostly section can shrinks vmlinux by 120 bytes.

# size vmlinux*
   text    data     bss     dec     hex filename
4835553  450210  610304 5896067  59f783 vmlinux.after_patch
4835553  450330  610304 5896187  59f7fb vmlinux.before_patch

Signed-off-by: Eric Dumazet <dada1@xxxxxxxxxxxxx>
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 5fee056..af48e86 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -256,14 +256,14 @@
  * The minimum number of bits of entropy before we wake up a read on
  * /dev/random.  Should be enough to do a significant reseed.
  */
-static int random_read_wakeup_thresh = 64;
+static int random_read_wakeup_thresh __read_mostly = 64;
 
 /*
  * If the entropy count falls under this number of bits, then we
  * should wake up processes which are selecting or polling on write
  * access to /dev/random.
  */
-static int random_write_wakeup_thresh = 128;
+static int random_write_wakeup_thresh __read_mostly = 128;
 
 /*
  * When the input pool goes over trickle_thresh, start dropping most