Removed `usbDelay(uint32_t cycles)`, added `usbSleep(uint32_t millis)`
The same method signature could cause silent code breakage at runtime,
as opposed to noisy code breakage at compile time which is the better
kind.
This patch adds calls to usbPoll in the progress callback. This
should address #98.
We call usbDelay instead of Poll, to call usbd_poll several times.
Otherwise it would only handle one event instead of handling all
events that were pending so far. The ugly magic number 5 is a guess.
Note that we also need to set usbTiny, so that we don't recursively
process messages. Since we don't know whether usbTiny is set, we
need to store the old value (especially true for u2f).
This fix also relies on another fix in libopencm3.
Holding confirm button at home screen asks user whether they wish to
lock the TREZOR (clear the cached PIN and passphrase and show the
screensaver). This is identical behaviour to the ClearSession message.
Following ECDH usage of layoutDecryptIdentity (which shows "GPG decrypt for:")
this commit adds a specific case for layoutSignIdentity, showing "GPG sign for:",
instead of "GPG login to:" (which is less appropriate in the GPG context).
According to specs, the display can handle up to 10 MHz SPI traffic
(minimum cycle time is 100 ns). This patch sets the SPI port to
7.5 MHz (60 MHz clock with divisor 8). In my tests the display works
even fine with SPI frequency at 60 MHz. I also minimized the delays
(the spec doesn't require a long setup time) and use the registers to
check when transfer is done instead of using a fixed delay.
This patch also changes the swipe function to swipe pixel by pixel.
Otherwise, the swipe would happen too fast to be seen.
This changes the display update time from 11 ms to 1.5 ms.
