docs: i2c: i2c-protocol: use proper names for ACK and NACK

Use the proper ACK and NACK naming from the I2C specification instead of
"accept" and "reverse accept".
Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/i2c/i2c-protocol.rst

@@ -11,7 +11,7 @@ Key to symbols
 S               Start condition
 P               Stop condition
 Rd/Wr (1 bit)   Read/Write bit. Rd equals 1, Wr equals 0.
-A, NA (1 bit)   Accept and reverse accept bit.
+A, NA (1 bit)   Acknowledge (ACK) and Not Acknowledge (NACK) bit
 Addr  (7 bits)  I2C 7 bit address. Note that this can be expanded as usual to
                 get a 10 bit I2C address.
 Comm  (8 bits)  Command byte, a data byte which often selects a register on