bcm2835-sdhost: Don't exit cmd wait loop on error

The FAIL flag can be set in the CMD register before command processing
is complete, leading to spurious "failed to complete" errors. This has
the effect of promoting harmless CRC7 errors during CMD1 processing
into errors that can delay and even prevent booting.

Also:
1) Convert the last KERN_ERROR message in the register dumping to
   KERN_INFO.
2) Remove an unnecessary reset call from  bcm2835_sdhost_add_host.

See: https://github.com/raspberrypi/linux/pull/1492



Signed-off-by: Phil Elwell <phil@raspberrypi.org>