iio: pressure: bmp280: Make time vars intuitive and move to fsleep

Move sleep functions to the new fsleep() implementation. While at it,
add time unit abbreviation as a suffix of time describing variables to
make them more intuitive.

Signed-off-by: Vasileios Amoiridis <vassilisamir@gmail.com>
Link: https://patch.msgid.link/20241202181907.21471-4-vassilisamir@gmail.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>