power: Hook up the readlink system call.

Change-Id: I28dcbd6fb3c54479eefea26d810d10c00195cc08
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/26830
Tested-by: Gem5 Cloud Project GCB service account <345032938727@cloudbuild.gserviceaccount.com>
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

src/arch/power/linux/process.cc

@@ -177,7 +177,7 @@ SyscallDescTable<PowerProcess::SyscallABI> PowerLinuxProcess::syscallDescs = {
     { 82, "reserved#82" },
     { 83, "symlink" },
     { 84, "unused#84" },
-    { 85, "readlink" },
+    { 85, "readlink", readlinkFunc },
     { 86, "uselib" },
     { 87, "swapon", gethostnameFunc },
     { 88, "reboot" },