platform: Clean up include header files

Adjust the order of include header files in alphabetical order in
platform codes. Also remove unnecessary inclusions.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>

platform/spike/platform.c

@@ -5,8 +5,8 @@
  */
 
 #include <sbi/sbi_platform.h>
-#include <sbi_utils/sys/htif.h>
 #include <sbi_utils/sys/clint.h>
+#include <sbi_utils/sys/htif.h>
 
 /* clang-format off */