Include <linux/vmalloc.h> explicitly on x86

Commit 1f059dfdf5d1 ("mm/vmalloc: Add empty <asm/vmalloc.h> headers
and use them from <linux/vmalloc.h>") restructured kernel header
dependencies since kernel v5.6-rc1, necessitating explicit inclusion
of <linux/vmalloc.h> on x86 architectures.

This ensures compatibility across kernel versions and prevents build
errors due to implicit declarations on kernels since v5.6-rc1.

Tested-by: Chisheng Chen <johnny1001s000602@gmail.com>
Co-authored-by: Po-Ying Chiu <charlie910417@gmail.com>

Author: EricccTaiwan

scripts/aspell-pws

@@ -177,3 +177,4 @@ kfifo
 PTR
 ttt
 tictactoe
+vmalloc

simrupt.c

@@ -9,6 +9,9 @@
 #include <linux/slab.h>
 #include <linux/version.h>
 #include <linux/workqueue.h>
+#if defined(CONFIG_X86)
+#include <linux/vmalloc.h>
+#endif
 
 MODULE_LICENSE("Dual MIT/GPL");
 MODULE_AUTHOR("National Cheng Kung University, Taiwan");