x86/um: Drop gate area handling

With the removal of the vDSO passthrough from the host,
FIXADDR_USER_START is always 0 and the gate area setup code is dead.

Remove it.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://patch.msgid.link/20251028-uml-remove-32bit-pseudo-vdso-v1-5-e930063eff5f@weissschuh.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Author: t-8ch

arch/um/include/asm/page.h

@@ -96,8 +96,4 @@ extern unsigned long uml_physmem;
 
 #endif	/* __ASSEMBLER__ */
 
-#ifdef CONFIG_X86_32
-#define __HAVE_ARCH_GATE_AREA 1
-#endif
-
 #endif	/* __UM_PAGE_H */

arch/x86/um/Makefile

@@ -13,7 +13,7 @@ obj-y = bugs_$(BITS).o delay.o fault.o \
 	ptrace.o ptrace_$(BITS).o ptrace_user.o setjmp_$(BITS).o signal.o \
 	stub_segv.o \
 	sys_call_table_$(BITS).o sysrq_$(BITS).o tls_$(BITS).o \
-	mem_$(BITS).o subarch.o os-Linux/
+	subarch.o os-Linux/
 
 ifeq ($(CONFIG_X86_32),y)
 
@@ -26,7 +26,7 @@ subarch-y += ../kernel/sys_ia32.o
 
 else
 
-obj-y += syscalls_64.o vdso/
+obj-y += mem_64.o syscalls_64.o vdso/
 
 subarch-y = ../lib/csum-partial_64.o ../lib/memcpy_64.o \
 	../lib/memmove_64.o ../lib/memset_64.o