scsi: isci: Fix infinite loop in while loop

In the case when the phy_mask is bitwise anded with the phy_index bit is
zero the continue statement currently jumps to the next iteration of the
while loop and phy_index is never actually incremented, potentially
causing an infinite loop if phy_index is less than SCI_MAX_PHS. Fix this
by turning the while loop into a for loop.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>