i2c-highlander: Trivial endian casting fixes

Fixes sparse warnings:
drivers/i2c/busses/i2c-highlander.c:95:26: warning: incorrect type in argument 1 (different base types)
drivers/i2c/busses/i2c-highlander.c:95:26:    expected restricted __be16 const [usertype] *p
drivers/i2c/busses/i2c-highlander.c:95:26:    got unsigned short [usertype] *<noident>
drivers/i2c/busses/i2c-highlander.c:106:15: warning: incorrect type in assignment (different base types)
drivers/i2c/busses/i2c-highlander.c:106:15:    expected unsigned short [unsigned] [short] [usertype] <noident>
drivers/i2c/busses/i2c-highlander.c:106:15:    got restricted __be16

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Ben Dooks <ben-linux@fluff.org>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Jean Delvare <khali@linux-fr.org>