staging: vchiq-core: get rid of is_master distinction

VCHIQ bulk transfers are what most people call DMA transfers. The CPU
sends a list of physical addresses to the VideoCore which then access
the memory directly without the need for CPU interaction.  With this
setup we call the CPU the "slave" and the VideoCore the "master".

There seems to be an option to switch roles in vchiq. Which nobody is
using nor is properly implemented. So we get rid of the "is_master == 1"
option, and all the related code.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>