[COMMITTED 2.41] ppc64le: Restore optimized strcmp and strncmp for power10

[Sachin Monga]

Backported the below 2 commits.

(cherry picked from commit 
2ea943f7d487d6a4166658b32af7c5365889fc34)

diff --git 
a/sysdeps/powerpc/powerpc64/le/power10/strncmp.S 
b/sysdeps/powerpc/powerpc64/le/power10/strncmp.S
new file mode 
100644
index 0000000000..6e09fcb7f2
--- /dev/null
+++ 
b/sysdeps/powerpc/powerpc64/le/power10/strncmp.S


(cherry picked from commit 9a40b1cda519cc4f532acb6d020390829df3d81b)

diff --git a/sysdeps/powerpc/powerpc64/le/power10/strcmp.S 
b/sysdeps/powerpc/powerpc64/le/power10/strcmp.S
new file mode 100644
index 0000000000..0d4a53317c
--- /dev/null
+++ b/sysdeps/powerpc/powerpc64/le/power10/strcmp.S