Fix logic errors in iwm_pcie_load_firmware_chunk introduced in r314065.

• There's no reason to have a while() loop here, because:
  • if msleep returns 0, that means we were woken up by the interrupt handler, and we are going to exit immediately as sc_fw_chunk_done will now be 1 (there is nothing else that sleeps on sc_fw.)
  • if msleep doesn't return 0 (i.e. it returned ETIMEDOUT) then we will exit immediately because of the if-test. So, just use a single msleep() and then check sc_fw_chunk_done as before.
• The comment said we were sleeping for 5 seconds, but the msleep was only for 1. Before r314065, this was 1 second and so was the comment, and in that commit the comment was changed and the function call wasn't.

Possibly fixes failures to initialize uCode on certain devices.

Submitted by: Augustin Cavalier (waddlesplash gmail.com)
Obtained from: Haiku 132990ecdcb072f2ce597b5d497ff3e5b1f09c20
MFC after: 10 days