ACPI / SBS: Add 5 us delay to fix SBS hangs on MacBook

Commit 7bc5a2bad0b8 'ACPI: Support _OSI("Darwin") correctly' caused
the MacBook firmware to expose the SBS, resulting in intermittent
hangs of several minutes on boot, and failure to detect or report
the battery.  Fix this by adding a 5 us delay to the start of each
SMBUS transaction.  This timing is the result of experimentation -
hangs were observed with 3 us but never with 5 us.

Fixes: 7bc5a2bad0b8 'ACPI: Support _OSI("Darwin") correctly'
Link: https://bugzilla.kernel.org/show_bug.cgi?id=94651
Signed-off-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Cc: 3.18+ <stable@vger.kernel.org> # 3.18+
[ rjw: Subject and changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>