static pie: fix building static PDE

static pie: fix building static PDE

When uclibc is built with static PIE support the _dl_load_base variable
shared between the libc-tls.c and reloc_static_pie.c creates the
dependency that requires linking reloc_static_pie.o into static
position-dependent executables resulting in the following build errors:
  gcc -static test.c -o test
  ...ld:
  ...usr/lib/libc.a(reloc_static_pie.os):(.text+0x0):
	undefined reference to `_DYNAMIC'

Move _dl_load_base definition to libc-tls.c to resolve this dependency
and fix static PDE build.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>