msm: ipa: replace usleep with udelay during disconnect procedure

If APPS enters suspend state during this usleep, the wakeup
is not guarenteed to happen in 100us as expected. This can cause
modem side to timeout waiting on APPS side response. Since order
of wait is only 100us, replace the sleep with a busy wait.

Change-Id: I8cebbd8723ad663c2ac9c081ac45422936c70fab
Signed-off-by: Ravi Gummadidala <rgummadi@codeaurora.org>