drivers/sensors: update upper->parsebuffer every new line

[chenzihan0416]

Summary

Fix GNSS NMEA parser buffer overflow handling by resetting parse position after error.

When the NMEA parser detects a buffer overflow (line exceeds GNSS_PARSE_BUFFERSIZE), it logs an error message but fails to reset parsenext to 0. This causes subsequent NMEA sentences to be appended to the corrupted buffer, leading to:

Continuous buffer overflow errors for all following sentences
Loss of valid GNSS data until the next '$' character is encountered
Potential memory corruption if overflow detection fails

Impact

Improves GNSS data reliability when receiving malformed or oversized NMEA sentences
Prevents data loss from cascading parse errors
No API or behavior changes for normal operation

Testing

nsh> echo "$GPGGA,<300_char_garbage...>*00" > /dev/ttyGNSS0
nsh> echo "$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47" > /dev/ttyGNSS0

before fix:

ERROR: NMEA buffer overflow, invalid statement:$GPGGA,<truncated>
ERROR: NMEA buffer overflow, invalid statement:GPGGA,123519,4807...
ERROR: NMEA buffer overflow, invalid statement:807.038,N,01131...
(repeating errors, no valid data parsed)

after fix:

ERROR: NMEA buffer overflow, invalid statement:$GPGGA,<truncated>
INFO: Parsed GPGGA: lat=48.1173, lon=11.5167, alt=545.4
(valid sentence parsed correctly after recovery)

[acassis]

@chenzihan0416 you don't need close the previous PR to fix it.

BTW, this one is wrong, you added a merge here. Please rebase with upstream to fix it.

[chenzihan0416]

@acassis : ( sorry, I encountered a problem when submitting the patch, which has now been rebased.