input: sensors: fix the bmp18x driver request regulator multiple times

The bmp18x driver may call regulator_get in resume routine. However,
regulator_get will call the sysfs APIs to create duplicated files
in sysfs. This will trigger the kernel warnings and backtrace.

Change-Id: I758f2866adae69fd8f8a9477c12aa714303ab6f2
Signed-off-by: Oliver Wang <mengmeng@codeaurora.org>