So far powerpc hw supported only one watchpoint. But Power10 is
introducing 2nd DAWR. Convert thread_struct->hw_brk into an array.
Signed-off-by: NRavi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
Reviewed-by: NMichael Neuling <mikey@neuling.org>
Link: https://lore.kernel.org/r/20200514111741.97993-10-ravi.bangoria@linux.ibm.com