x86/oprofile: Avoid TIF_IA32 when checking 64bit mode

In preparation to remove TIF_IA32, stop using it in oprofile code. Use
user_64bit_mode() instead.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20201004032536.1229030-4-krisman@collabora.com