Update iphone 15 pro benchmarking numbers (#2927)

Summary:

ATT

Created from CodeHub with https://fburl.com/edit-in-codehub

Differential Revision: D55895703

Author: kimishpatel

examples/models/llama2/README.md

@@ -39,7 +39,7 @@ Performance was measured on Samsung Galaxy S22, S23, S24 and One Plus 12. Measur
 |Galaxy S22 | 8.15 tokens/second | 8.3 tokens/second |
 |Galaxy S24 | 10.66 tokens/second | 11.26 tokens/second |
 |One plus 12 | 11.55 tokens/second | 11.6 tokens/second |
-|iPhone 15 pro | x | x |
+|iPhone 15 pro | ~6 tokens/second | ~6 tokens/second |
 
 
 # Instructions