mem: Eliminate the now unused GENERIC_IPR request flag.

Jira Issue: https://gem5.atlassian.net/browse/GEM5-187

Change-Id: Id3aaffa4fa88032fd209c5c3b6f67283a6af1c48
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/23187
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Reviewed-by: Muhammad Sarmad Saeed <mssaeed@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

src/mem/request.hh

@@ -172,12 +172,6 @@ class Request
           */
         KERNEL                      = 0x00001000,
 
-        /**
-         * The request should be handled by the generic IPR code (only
-         * valid together with MMAPPED_IPR)
-         */
-        GENERIC_IPR                 = 0x08000000,
-
         /** The request targets the secure memory space. */
         SECURE                      = 0x10000000,
         /** The request is a page table walk */