x86/boot/e820: Avoid overwriting e820_table_firmware

The following commit in 2013:

  77ea8c94 ("x86: Reserve setup_data ranges late after parsing memmap cmdline")

has fixed the issue of losing setup_data information by deferring the
e820_reserve_setup_data() call until the early params have been parsed.

But this also introduced a new problem that, during early params parsing,
the kexec kernel might fake a mptable and saves it into the e820_table_firmware[]
table (without saving the mptable to the e820_table[]), however the subsequent
invoking of e820_reserve_setup_data() will overwrite the e820_table_firmware[]
according to the e820_table[], thus the fake mptable information is lost.

Fix this issue by updating the e820_table_firmware[] according to
the setup_data information, but without overwriting it.

Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Xunlei Pang <xlpang@redhat.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>