um: Remove unused user_context function

It's no longer used since commit 6aa802c ("uml: throw out
CHOOSE_MODE").

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20241128083137.2219830-10-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Author: btw616

arch/um/kernel/process.c

@@ -213,14 +213,6 @@ int __uml_cant_sleep(void) {
 	/* Is in_interrupt() really needed? */
 }
 
-int user_context(unsigned long sp)
-{
-	unsigned long stack;
-
-	stack = sp & (PAGE_MASK << CONFIG_KERNEL_STACK_ORDER);
-	return stack != (unsigned long) current_thread_info();
-}
-
 extern exitcall_t __uml_exitcall_begin, __uml_exitcall_end;
 
 void do_uml_exitcalls(void)

arch/x86/um/shared/sysdep/ptrace.h

@@ -74,8 +74,6 @@ struct uml_pt_regs {
 #define UPT_FAULTINFO(r) (&(r)->faultinfo)
 #define UPT_IS_USER(r) ((r)->is_user)
 
-extern int user_context(unsigned long sp);
-
 extern int arch_init_registers(int pid);
 
 #endif /* __SYSDEP_X86_PTRACE_H */