include/net/inet_connection_sock.h: Use pr_devel() instead of pr_debug()

When DYNAMIC_DEBUG enabled, pr_debug() depends on KBUILD_MODNAME which
also depends on the modules name in Makefile.
Refer to the information in "scripts/Makefile.lib":

 # $(modname_flags) #defines KBUILD_MODNAME as the name of the module it will
 # end up in (or would, if it gets compiled in)
 # Note: Files that end up in two or more modules are compiled without the
 #       KBUILD_MODNAME definition. The reason is that any made-up name would
 #       differ in different configs.

File "inet_connection_sock.h" is a common share header that not can 
be use for one module, so use pr_devel instead of pr_debug is OK.

In file included from include/linux/printk.h:277:0,
                 from include/linux/kernel.h:13,
                 from include/linux/list.h:8,
                 from include/linux/kobject.h:20,
                 from include/linux/device.h:17,
                 from include/rdma/ib_verbs.h:43,
                 from /usr/src/drbd-9.0/drbd/drbd-kernel-compat/tests/have_ib_cq_init_attr.c:1:
include/net/inet_connection_sock.h: In function ‘inet_csk_clear_xmit_timer’:
include/linux/dynamic_debug.h:66:14: error: ‘KBUILD_MODNAME’ undeclared (first use in this function)
   .modname = KBUILD_MODNAME,   \
              ^
include/linux/dynamic_debug.h:76:2: note: in expansion of macro ‘DEFINE_DYNAMIC_DEBUG_METADATA’
  DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, fmt);  \
  ^
include/linux/printk.h:283:2: note: in expansion of macro ‘dynamic_pr_debug’
  dynamic_pr_debug(fmt, ##__VA_ARGS__)
  ^
include/net/inet_connection_sock.h:213:3: note: in expansion of macro ‘pr_debug’
   pr_debug("%s", inet_csk_timer_bug_msg);
   ^

Signed-off-by: Nick Wang <nwang@suse.de>
---
 include/net/inet_connection_sock.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

From: Nick Wang <nwang@suse.com>
Date: Tue,  8 Mar 2016 13:52:28 +0800

> File "inet_connection_sock.h" is a common share header that not can 
> be use for one module, so use pr_devel instead of pr_debug is OK.

Not really, we only want these printks to do anything only when debug
printk's are enabled.

We don't want the overhead otherwise.

You'll need to find another fix for this, sorry.