modutils: remove special handling of uClibc

modutils: remove special handling of uClibc

Commit 3a45b87ac36f (modutils: support finit_module syscall) introduced
macro finit_module. But it is not defined for uClibc.

The compilation for busybox fails for MIPS with:
With uClibc, we get following build errors:

  modutils/lib.a(modutils.o): In function `bb_init_module':
  modutils.c:(.text.bb_init_module+0x94): undefined reference to `finit_module'
  modutils.c:(.text.bb_init_module+0xa0): undefined reference to `finit_module'

We can just use syscall() without any need for the
uClibc wrappers.

Newer versions of uClibc-ng (>1.0.20) will remove the
module syscall wrappers.

Found via Buildroot autobuilders:
http://autobuild.buildroot.net/results/556/55655daef23788fb3967f801ec8b79e9bed7122b/build-end.log

function                                             old     new   delta
bb_delete_module                                      26      32      +6
bb_init_module                                        90      95      +5
delete_module                                         37       -     -37
init_module                                           53       -     -53
------------------------------------------------------------------------------
(add/remove: 0/4 grow/shrink: 2/0 up/down: 11/-90)            Total: -79 bytes

Reported-by: Rahul Bedarkar <rahul.bedarkar@imgtec.com>
Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>