mailbox/bcm2835: Fix mailbox full detection.
mailbox/bcm2835: Fix mailbox full detection.

With the VC reader blocked and the ARM writing, MAIL0_STA reads empty
permanently while MAIL1_STA goes from empty (0x40000000) to non-empty
(0x00000001-0x00000007) to full (0x80000008).

This bug ended up having no effect on us, because all of our
transactions in the client driver were synchronous and under a mutex.

Suggested-by: Phil Elwell <e888d2bd6f13f82caa51a37c03d034c76f661ba3@raspberrypi.org>
Signed-off-by: Eric Anholt <96f164ad4d9b2b0dacf8ebee2bb1eeb3aa69adf1@anholt.net>
Acked-by: Stephen Warren <5ef2a23ba3aff51d1cfc8c113c1ec34b608b3b13@wwwdotorg.org>
Signed-off-by: Jassi Brar <191fbc354bb0d45dfb103e8f4f6583bfe2bb3ef7@linaro.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs