staging: vchiq_arm: Avoid long udelay

vchiq_initialise() is used in non-interrupt context, so we can
replace udelay with usleep_range as suggested by timers-howto.txt.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>