[peripherals] mpu60x0: use gcc pragma to ignore cast-qual warnings

The buffer is volatile, since filled from ISR...
But we know it's ok to use it here so we silence the warning.

Also there is a bug in some gcc version that incorrectly reports this as
peripherals/mpu60x0_spi.c:118:33: warning: cast discards '__attribute__((noreturn))' qualifier from pointer target type [-Wcast-qual]
see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55383
[peripherals] ignore cast-qual for mpu9250 as well
Merge pull request #946 from paparazzi/mpu60x0_ignore_cast_warning

[peripherals] mpuxxxx: use gcc pragma to ignore cast-qual warnings

The buffer is volatile, since filled from ISR...
But we know it's ok to use it here so we silence the warning.

Also there is a bug in some gcc version that incorrectly reports this as
peripherals/mpu60x0_spi.c:118:33: warning: cast discards '__attribute__((noreturn))' qualifier from pointer target type [-Wcast-qual]
see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55383
[ms5611] Fix baro i2c transactions

Since the simple i2c driver for linux does busy waiting on i2c_submit (and not queue a new transaction),
setting the transaction status to done at the end (with a new transcaction in between) will set the status
of the wrong transaction...

Did not seem happen with the other i2c implementations (lpc21, stm32) so far, but since they add the transaction
to the queue which is handled in the I2C ISR, it could also happen there (race condition).

closes #960