x86: Move find_smp_config() earlier and avoid bootmem usage

Move the find_smp_config() call to before bootmem is initialized.
Use reserve_early() instead of reserve_bootmem() in it.

This simplifies the code, we only need to call find_smp_config()
once and can remove the now unneeded reserve parameter from
x86_init_mpparse::find_smp_config.

We thus also reduce x86's dependency on bootmem allocations.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <4B0BB9F2.70907@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>