hppa/vdso: Provide 64-bit clock_gettime() vDSO only

Adhemerval noticed that the gettimeofday() and 32-bit clock_gettime()
vDSO calls won't be used by glibc on hppa, so there is no need to
declare them.  Both syscalls will be emulated by utilizing return values
of the 64-bit clock_gettime() vDSO instead.

Signed-off-by: Helge Deller <deller@gmx.de>
Suggested-by: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>