bcma: use bcma_debug and pr_cont in MIPS driver

Using bcma_debug gives a device-specific prefix for messages and pr_cont
is a common helper for continuing a line.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Acked-By: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>