drm_hwcomposer: Remove hardcoded PAGE_SIZE usage in gralloc_helper

Use getpagesize() to make drm_hwcomposer work with multiple page sizes.
This benefits Android as AOSP no longer relies on bionic's PAGE_SIZE
macro.

Bug: 310232825
Test: Presubmit
Signed-off-by: Vilas Bhat <vilasbhat@google.com>

Change-Id: I9af7436ac9ca6c052f67cdd296a960b51b8ba67a
diff --git a/tests/test_include/gralloc_helper.h b/tests/test_include/gralloc_helper.h
index b6cd24d..9741c33 100644
--- a/tests/test_include/gralloc_helper.h
+++ b/tests/test_include/gralloc_helper.h
@@ -47,7 +47,8 @@
 
 static inline size_t round_up_to_page_size(size_t x)
 {
-	return (x + (PAGE_SIZE - 1)) & ~(PAGE_SIZE - 1);
+	const size_t page_size = getpagesize();
+	return (x + (page_size - 1)) & ~(page_size - 1);
 }
 
 #endif /* GRALLOC_HELPER_H_ */