powerpc/64: Drop unnecessary 'rc' variable

Simplify the code to enhance readability and maintain a consistent
coding style.

Signed-off-by: Xichao Zhao <zhao.xichao@vivo.com>
Acked-by: Gautam Menghani <gautam@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250801035908.370463-1-zhao.xichao@vivo.com