configure: move HAVE_LINUX_INPUT_H to CheckInputEvents()

c.f.: https://github.com/libsdl-org/SDL/pull/8459.
Ref. issue https://github.com/libsdl-org/SDL/issues/8450

configure

@@ -18942,12 +18942,6 @@ if test "x$ac_cv_header_signal_h" = xyes
 then :
   printf "%s\n" "#define HAVE_SIGNAL_H 1" >>confdefs.h
 
-fi
-ac_fn_c_check_header_compile "$LINENO" "linux/input.h" "ac_cv_header_linux_input_h" "$ac_includes_default"
-if test "x$ac_cv_header_linux_input_h" = xyes
-then :
-  printf "%s\n" "#define HAVE_LINUX_INPUT_H 1" >>confdefs.h
-
 fi
 
 
@@ -26434,6 +26428,9 @@ rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
 printf "%s\n" "$use_input_events" >&6; }
         if test x$use_input_events = xyes; then
 
+printf "%s\n" "#define HAVE_LINUX_INPUT_H 1" >>confdefs.h
+
+
 printf "%s\n" "#define SDL_INPUT_LINUXEV 1" >>confdefs.h
 
             SUMMARY_input="${SUMMARY_input} linuxev"

configure.ac

@@ -330,7 +330,7 @@ if test x$enable_libc = xyes; then
 dnl Check for C library headers
 dnl AC_CHECK_INCLUDES_DEFAULT is an autoconf-2.7x thing where AC_HEADER_STDC is deprecated.
     m4_ifdef([AC_CHECK_INCLUDES_DEFAULT], [AC_CHECK_INCLUDES_DEFAULT], [AC_HEADER_STDC])
-    AC_CHECK_HEADERS(sys/types.h stdio.h stdlib.h stddef.h stdarg.h malloc.h memory.h string.h strings.h wchar.h inttypes.h stdint.h limits.h ctype.h math.h float.h iconv.h signal.h linux/input.h)
+    AC_CHECK_HEADERS(sys/types.h stdio.h stdlib.h stddef.h stdarg.h malloc.h memory.h string.h strings.h wchar.h inttypes.h stdint.h limits.h ctype.h math.h float.h iconv.h signal.h)
 
 dnl Check for typedefs, structures, etc.
     AC_TYPE_SIZE_T
@@ -2769,6 +2769,7 @@ dnl Check for Linux 2.4 unified input event interface support
         ]])], [use_input_events=yes],[])
         AC_MSG_RESULT($use_input_events)
         if test x$use_input_events = xyes; then
+            AC_DEFINE(HAVE_LINUX_INPUT_H, 1, [ ])
             AC_DEFINE(SDL_INPUT_LINUXEV, 1, [ ])
             SUMMARY_input="${SUMMARY_input} linuxev"
         fi