firewire: ohci: lazy bus time initialization
firewire: ohci: lazy bus time initialization

The Bus_Time CSR is virtually never used, so we can avoid burning CPU in
interrupt context for 1 or 3 IsochronousCycleTimer accesses every minute
by not tracking the bus time until the CSR is actually accessed for the
first time.

Signed-off-by: Clemens Ladisch <9f57ef5ff1095f40b1ee8b7caa363908baef59d7@ladisch.de>
Signed-off-by: Stefan Richter <fbd796546fc801b34e01e453c6fd30283e012038@s5r6.in-berlin.de>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas