touchpad_st: fix bug in dump_memory
touchpad_st: fix bug in dump_memory

in dump_memory, rx_len includes DUMMY_BYTE, but it should not be counted
when we are printing.

BRANCH=nocturne
BUG=b:117398324
TEST=manual on whiskers
Signed-off-by: Wei-Han Chen <5413a119f383c3f4549c3ef659403f393bf06e9d@chromium.org>

Change-Id: I9810e97b1fb0ce94973fc24963d6c6ea601759be
Reviewed-on: https://chromium-review.googlesource.com/1267875
Commit-Ready: Wei-Han Chen <5413a119f383c3f4549c3ef659403f393bf06e9d@chromium.org>
Tested-by: Wei-Han Chen <5413a119f383c3f4549c3ef659403f393bf06e9d@chromium.org>
Reviewed-by: Nicolas Boichat <f3daba1cdc403799935674d3cd4b0e5bd1804232@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec