powerpc/machdep: Remove duplicated include in svm.c

The header files linux/mem_encrypt.h is included twice in svm.c,
so one inclusion of each can be removed.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=11750


Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20241107010259.46308-1-yang.lee@linux.alibaba.com