drivers: sensor: bmi08x: fix interfaceand trigger

1. Temperature Interface
According to BMI08x datasheet, temperature reading
requires both MSB and LSB bytes to be read and
processed correctly.

Temp data processing should follow the formula:
Temp in °C = (temp_msb * 8) + (temp_lsb / 32)

This patch implements the correct reading
sequence and calculation method as specified
in the datasheet.

2. Trigger Setting
Previously we set handler and then trigger struct.
However under some situation, as long as we set
the handler, we get into ISR immediately and never
set trigger struct.
I simply changed the sequence.

Testing:
- Verified temperature readings match datasheet
- Tested on stm32f407igh board with BMI08x sensor

Fixes: #82375

Signed-off-by: Wenxi Xu <xuwenxi0517@gmail.com>