net: nvethernet: Use conftest for Linux v6.6

In Linux v6.6, the header net/page_pool.h was split into two headers;
net/page_pool/helper.h and net/page_pool/types.h. Use the conftest
script to detect which of these headers are present and generate compile
time definitions for including the appropriate headers.

Bug 4346767

Change-Id: I389ce5b867a1efd867b8392bb21383784c1b4af6
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nv-oot/+/3026553
(cherry picked from commit cd4dce2c20)
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nv-oot/+/3028310
Reviewed-by: Laxman Dewangan <ldewangan@nvidia.com>
GVS: Gerrit_Virtual_Submit <buildbot_gerritrpt@nvidia.com>

scripts/conftest/Makefile

@@ -159,7 +159,8 @@ NV_HEADER_PRESENCE_TESTS = \
   generated/autoconf.h \
   linux/kconfig.h \
   linux/iosys-map.h \
-  net/gso.h
+  net/gso.h \
+  net/page_pool.h
 
 # Filename to store the define for the header in $(1); this is only consumed by
 # the rule below that concatenates all of these together.