bcm43xx_debugfs sscanf fix

ia64:

drivers/net/wireless/bcm43xx/bcm43xx_debugfs.c: In function `tsf_write_file':
drivers/net/wireless/bcm43xx/bcm43xx_debugfs.c:237: warning: long long int format, u64 arg (arg 3)
drivers/net/wireless/bcm43xx/bcm43xx_debugfs.c:237: warning: long long int format, u64 arg (arg 3)

We do not know what type was used to implement u64 and we can never use u64 in
printk(), sscanf(), etc.

Cc: Michael Buesch <mb@bu3sch.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>