nptl: Fix libpthread build when UCLIBC_LINUX_SPECIFIC is disabled

nptl: Fix libpthread build when UCLIBC_LINUX_SPECIFIC is disabled

NPTL library needs both madvise and statfs symbols, that are guarded
by UCLIBC_LINUX_SPECIFIC option. This fix provides these symbols too
when NPTL is used, indipendently by UCLIBC_LINUX_SPECIFIC choice.
Otherwise libpthread link fails as below:

LD libpthread-0.9.32-git.so
libpthread/nptl/libpthread_so.a(pthread_create.oS): In function `__free_tcb':
pthread_create.c:(.text+0x1184): undefined reference to `madvise'
libpthread/nptl/libpthread_so.a(sem_open.oS): In function `__where_is_shmfs':
sem_open.c:(.text+0x764): undefined reference to `statfs'
collect2: ld returned 1 exit status
make: *** [lib/libpthread.so] Error 1

Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>