Revert "cmake: fold HAVE_INPUT_EVENTS into HAVE_LINUX_INPUT_H"

This reverts commit 01eb30549310591ce520f6ebe19f68eb52a14c92.

CMakeLists.txt

@@ -1034,6 +1034,7 @@ if(SDL_LIBC)
       string(REGEX REPLACE "[./]" "_" _HAVE_H ${_UPPER})
       check_include_file("${_HEADER}" ${_HAVE_H})
     endforeach()
+    check_include_file(linux/input.h HAVE_LINUX_INPUT_H)
 
     set(STDC_HEADER_NAMES "stddef.h;stdarg.h;stdlib.h;string.h;stdio.h;wchar.h;float.h")
     check_include_files("${STDC_HEADER_NAMES}" STDC_HEADERS)
@@ -1478,7 +1479,7 @@ elseif(UNIX AND NOT APPLE AND NOT RISCOS AND NOT HAIKU)
         #ifndef EVIOCGNAME
         #error EVIOCGNAME() ioctl not available
         #endif
-        int main(int argc, char** argv) { return 0; }" HAVE_LINUX_INPUT_H)
+        int main(int argc, char** argv) { return 0; }" HAVE_INPUT_EVENTS)
 
     if(LINUX)
       check_c_source_compiles("
@@ -1514,11 +1515,11 @@ elseif(UNIX AND NOT APPLE AND NOT RISCOS AND NOT HAIKU)
           }" HAVE_INPUT_WSCONS)
     endif()
 
-    if(HAVE_LINUX_INPUT_H)
+    if(HAVE_INPUT_EVENTS)
       set(SDL_INPUT_LINUXEV 1)
     endif()
 
-    if(SDL_HAPTIC AND HAVE_LINUX_INPUT_H)
+    if(SDL_HAPTIC AND HAVE_INPUT_EVENTS)
       set(SDL_HAPTIC_LINUX 1)
       file(GLOB HAPTIC_SOURCES ${SDL2_SOURCE_DIR}/src/haptic/linux/*.c)
       list(APPEND SOURCE_FILES ${HAPTIC_SOURCES})
@@ -1611,7 +1612,7 @@ elseif(UNIX AND NOT APPLE AND NOT RISCOS AND NOT HAIKU)
       list(APPEND SOURCE_FILES "${SDL2_SOURCE_DIR}/src/core/linux/SDL_udev.c")
     endif()
 
-    if(HAVE_LINUX_INPUT_H)
+    if(HAVE_INPUT_EVENTS)
       list(APPEND SOURCE_FILES "${SDL2_SOURCE_DIR}/src/core/linux/SDL_evdev.c")
       list(APPEND SOURCE_FILES "${SDL2_SOURCE_DIR}/src/core/linux/SDL_evdev_kbd.c")
     endif()