powerpc: Fix static-linked version of __ppc_get_timebase_freq [BZ #24640]

powerpc: Fix static-linked version of __ppc_get_timebase_freq [BZ #24640]

__ppc_get_timebase_freq() always return 0 when using static linked
glibc.

This is a minimal example.c to reproduce:

    /******************************/
    #include <inttypes.h>
    #include <stdint.h>
    #include <stdio.h>
    #include <sys/platform/ppc.h>

    int main() {
        uint64_t freq = __ppc_get_timebase_freq();
        printf("Time Base frequency = %"PRIu64" Hz\n", freq);
        if (freq == 0)
            return -1;
        return 0;
    }
    /******************************/

Compile command: gcc -static example.c

This bug has been reproduced, fixed and tested on all powerpc platforms
(ppc32, ppc64 and ppc64le).

The underlying code of __ppc_get_timebase_freq uses __get_timebase_freq
that has a different implementation for shared and static version of
glibc.  In the static version, there is an incorrect sense in the if
check for the fd returned when opening /proc/cpuinfo.

This solution is mostly a cherry-pick from:

  commit 4791e4f773d060c1a37b27aac5b03cdfa9327afc
  Author: Stan Shebs <stanshebs@google.com>
  Date:   Fri May 17 12:25:19 2019 -0700
  Subject: Fix sense of a test in the static-linking version of ppc get_clockfreq

That is in branch glibc/google/grte/v5-2.27/master and was mentioned for
inclusion on master here:

  https://www.sourceware.org/ml/libc-alpha/2019-05/msg00409.html

Adapted from original fix for get_clockfreq. That code was moved to
get_timebase_freq.

Also added a static-build testcase for __ppc_get_timebase_freq since the
underlying function has different implementations for shared and static
build.

	[BZ #24640]
	* sysdeps/unix/sysv/linux/powerpc/get_timebase_freq.c
	[!SHARED] (__get_timebase_freq): Fix sense of a test in the
	static-linking version.
	* sysdeps/unix/sysv/linux/powerpc/Makefile
	(tests-static): Add test-gettimebasefreq-static.
	(tests): Likewise.
	* sysdeps/unix/sysv/linux/powerpc/test-gettimebasefreq-static.c:
	New file.