Remove PAGE_SIZE call sites.

To enable experiments with non-4KiB page sizes, introduce
an inline page_size() function that will either return the runtime
page size (if PAGE_SIZE is not 4096) or a constant 4096 (elsewhere).
This should ensure that there are no changes to the generated code on
unaffected platforms.

Test: source build/envsetup.sh
      lunch aosp_cf_arm64_16k_phone-userdebug
      m -j32 installclean
      m -j32
Test: launch_cvd \
  -kernel_path /path/to/out/android14-5.15/dist/Image \
  -initramfs_path /path/to/out/android14-5.15/dist/initramfs.img \
  -userdata_format=ext4
Bug: 277272383
Bug: 230790254
Change-Id: Ic0ed98b67f7c6b845804b90a4e16649f2fc94028
diff --git a/linker/linker_mapped_file_fragment.cpp b/linker/linker_mapped_file_fragment.cpp
index cbe5f66..6be1b2b 100644
--- a/linker/linker_mapped_file_fragment.cpp
+++ b/linker/linker_mapped_file_fragment.cpp
@@ -29,6 +29,7 @@
 #include "linker_mapped_file_fragment.h"
 #include "linker_debug.h"
 #include "linker_utils.h"
+#include "platform/bionic/page.h"
 
 #include <inttypes.h>
 #include <stdlib.h>