um: Remove duplicate arch.h header

./arch/um/kernel/trap.c: arch.h is included more than once.

Reported-by: Abaci Robot <[email protected]>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=19877
Signed-off-by: Jiapeng Chong <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Johannes Berg <[email protected]>

Author: Jiapeng Chong

arch/um/kernel/trap.c

@@ -16,7 +16,6 @@
 #include <kern_util.h>
 #include <os.h>
 #include <skas.h>
-#include <arch.h>
 
 /*
  * Note this is constrained to return 0, -EFAULT, -EACCES, -ENOMEM by