Hi!
[ Upstream commit a139ffa40f0c24b753838b8ef3dcf6ad10eb7854 ]
Reading from the chip should be unlocked on error path else the lock
could never being released.
Fixes: 07914c84ba30 ("iio: adc: Add driver for Microchip MCP3422/3/4 high resolution ADC")
Fixes: 3f1093d83d71 ("iio: adc: mcp3422: fix locking scope")
Well, 3f1093d83d71 is only applied later in the stable series, so this
introduces spurious unlock.
Ideally this should go just after 3f1093d83d71 ("iio: adc: mcp3422:
fix locking scope").