bfd: Fix objdump --dynamic-reloc for SPARC 64-bit to show symbol names.

Fixes ld/testsuite/ld-elf/shared.exp "Build libpr16496b.so".

The root cause is in bfd/elf64-sparc.c, elf64_sparc_slurp_one_reloc_table(),
bfd_get_symcount() was used for dynamic mode as well. The fix is to use
bfd_get_dynamic_symcount().

This has been tested with sparc64-linux-gnu, and it does not introduce any
regressions.

bfd/ChangeLog:

2017-02-06  Sheldon Lobo  <sheldon.lobo@oracle.com>

	Fix sparc64 dynamic relocation processing to use the dynamic
        symbol count.
	* elf64-sparc.c (elf64_sparc_slurp_one_reloc_table): Use 'dynamic'
	to determine if bfd_get_symcount() or bfd_get_dynamic_symcount()
	should be used.