powerpc/perf: Fix MMCRA_BHRB_DISABLE define for binutils < 2.28

Commit 9908c826 ("powerpc/perf: Add Power10 PMU feature to DT CPU
features") defines MMCRA_BHRB_DISABLE as `0x2000000000UL`. Binutils
version less than 2.28 doesn't support UL suffix.

  arch/powerpc/kernel/cpu_setup_power.S: Assembler messages:
  arch/powerpc/kernel/cpu_setup_power.S:250: Error: found 'L', expected: ')'
  arch/powerpc/kernel/cpu_setup_power.S:250: Error: junk at end of line, first unrecognized character is `L'
  arch/powerpc/kernel/cpu_setup_power.S:250: Error: found 'L', expected: ')'
  arch/powerpc/kernel/cpu_setup_power.S:250: Error: found 'L', expected: ')'
  arch/powerpc/kernel/cpu_setup_power.S:250: Error: junk at end of line, first unrecognized character is `L'
  arch/powerpc/kernel/cpu_setup_power.S:250: Error: found 'L', expected: ')'
  arch/powerpc/kernel/cpu_setup_power.S:250: Error: found 'L', expected: ')'
  arch/powerpc/kernel/cpu_setup_power.S:250: Error: operand out of range (0x0000002000000000 is not between 0xffffffffffff8000 and 0x000000000000ffff)

Fix this by wrapping it with the `_UL` macro.

Fixes: 9908c826 ("Add Power10 PMU feature to DT CPU features")
Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Reviewed-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1595996214-5833-1-git-send-email-atrajeev@linux.vnet.ibm.com