x86/headers: Remove unnecessary #include <asm/export.h>

There is no EXPORT_SYMBOL() line there, hence #include <asm/export.h>
is unnecessary.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230806145958.380314-1-masahiroy@kernel.org

arch/x86/entry/vdso/vsgx.S

 /* SPDX-License-Identifier: GPL-2.0 */
 
 #include <linux/linkage.h>
-#include <asm/export.h>
 #include <asm/errno.h>
 #include <asm/enclu.h>