Rename fields in the struct wrsTemperature_s to reflect SNMP objects'
names.

temp_fpga -> wrsTempFPGA
temp_pll -> wrsTempPLL
temp_psl -> wrsTempPSL
temp_psr -> wrsTempPSR
temp_fpga_thold -> wrsTempThresholdFPGA
temp_pll_thold -> wrsTempThresholdPLL
temp_psl_thold -> wrsTempThresholdPSL
temp_psr_thold -> wrsTempThresholdPSR

Signed-off-by: Adam Wujek <adam.wujek@cern.ch>