GCC correctly points out that on 32-bit kernels, e820_search_gap()
not finding a start now leads to pci_mem_start ('gapstart') being set to an
uninitialized value:

  arch/x86/kernel/e820.c: In function 'e820_setup_gap':
  arch/x86/kernel/e820.c:641:16: error: 'gapstart' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This restores the behavior from before this cleanup:

  b4ed1d15 ("x86/e820: Make e820_search_gap() static and remove unused variables")

... defaulting to address 0x10000000 if nothing was found.
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Fixes: b4ed1d15 ("x86/e820: Make e820_search_gap() static and remove unused variables")
Link: http://lkml.kernel.org/r/20170111144926.695369-1-arnd@arndb.deSigned-off-by: NIngo Molnar <mingo@kernel.org>