[llvm] Revert "[llvm-exegesis][AArch64] Disable pauth and ldgm as unsupported instructions fixed (#136868)" (PR #142382)

[Abhilash Majumder via llvm-commits]

================
@@ -12,12 +12,6 @@
 #if defined(__aarch64__) && defined(__linux__)
 #include <linux/prctl.h> // For PR_PAC_* constants
----------------
abhilash1910 wrote:

I think this header is duplicated in sys/prctl.h ; but sure we can keep it and remove safely in my PR. Thanks

https://github.com/llvm/llvm-project/pull/142382