sky2: memory barriers change
sky2: memory barriers change

Do some memory barrier changes for safety/perfomance:
Don't need read after update to index, mmiowb() followed by read at end
of irq is sufficient.

Signed-off-by: Stephn Hemminger <a072e933f45880fe04500ea083d5c7f6e81a06f0@linux-foundation.org>
Signed-off-by: Jeff Garzik <f3e731dfa293c7a83119d8aacfa41b5d2d780be9@garzik.org>

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