The maximum size of ATR_REQ and ATR_RES is 64 bytes.
The maximum number of General Bytes is calculated by
the maximum number of data bytes in the ATR_REQ/ATR_RES,
substracted by the number of mandatory data bytes.

ATR_REQ: 16 mandatory data bytes, giving a maximum of
48 General Bytes.
ATR_RES: 17 mandatory data bytes, giving a maximum of
47 General Bytes.

Regression introduced in commit a99903ec.
Signed-off-by: Julien Lefrique <lefrique@marvell.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>