touchcal-conv: Increase udev rule timeout to 15s

On SANTINO with AD7879 we observed that the /etc/shared/pointercal is only available quite late.

Increasing the timeout to 25 and the verbosity I get the following output out of the touchcal-conv started by the udev rule:

Open touch device /dev/input/event0
Touch 'AD7879 Touchscreen'
Absolute axis X [0..4095]
Absolute axis Y [0..4095]
Waiting for /etc/shared/pointercal (25s)
Waiting for /etc/shared/pointercal (24s)
Waiting for /etc/shared/pointercal (23s)
Waiting for /etc/shared/pointercal (22s)
Waiting for /etc/shared/pointercal (21s)
Waiting for /etc/shared/pointercal (20s)
Waiting for /etc/shared/pointercal (19s)
Waiting for /etc/shared/pointercal (18s)
Waiting for /etc/shared/pointercal (17s)
Waiting for /etc/shared/pointercal (16s)
Waiting for /etc/shared/pointercal (15s)
Opening /etc/shared/pointercal as pointercal
Read 53 bytes from pointercal: -33 -13310 53215504 -8294 51 32767950 65536 800 480 0
Decode Matrix from -33 -13310 53215504 -8294 51 32767950 65536 800 480 0
Linear calibration constants (tslib):
             -33
          -13310
        53215504
           -8294
              51
        32767950
           65536

Cal resolution 800x480
Rotation (unused) 0
Linear calibration constants (libinput):
        -0.00258
        -1.03959
        1.01501
        -1.07968
        0.00664
        1.04167

I conclude that the pointercal is not available for ~10 seconds. I have not analyzed the reason for this delay any further. Thus increase the timeout to 15s.

BCS 746-000567

See also https://projekte/bcs/requirementdetail/main/display?oid=1636877860989_JRequirement