i2c: qup: remove redundant variables for BAM SG count

i2c: qup: remove redundant variables for BAM SG count

The rx_nents and tx_nents are redundant. rx_buf and tx_buf can
be used for total number of SG entries. Since rx_buf and tx_buf
give the impression that it is buffer instead of count so rename
it to tx_cnt and rx_cnt for giving it more meaningful variable
name.

Signed-off-by: Abhishek Sahu <[email protected]>
Reviewed-by: Austin Christ <[email protected]>
Reviewed-by: Andy Gross <[email protected]>
Signed-off-by: Wolfram Sang <[email protected]>