Staging: bcm: Clean up code in ioctl: IOCTL_BCM_EEPROM_REGISTER_READ

This patch verifies two conditions before executing
a kmalloc call. First, it checks to see that
IoBuffer.OutputLength is not greater than an
unsigned short. If so, an invalid value may be
returned. The second change is a check to make
sure IoBuffer.OutputLength is not equal to
zero. Which simply keeps this code inline with
the other ioctl, IOCTL_BCM_REGISTER_READ_PRIVATE.

Signed-off-by: Kevin McKinney <klmckinney1@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>