sunxi: mali: Drop SUNXI_MALI_RESERVED_MEM option

This option was only providing a 64MB boot time memory
reservation for Mali GPU. That's a mostly useless waste
of memory on the devices with only 512MB of RAM (such
as A10-OLinuXino-LIME).

Moreover, the "sunxi_no_mali_mem_reserve" kernel cmdline
option (implemented as part of this code) was unsafe and
allowed the unsuspecting users to cause memory corruption
and take down the system by just modprobing the mali kernel
module.

Because the Mali400 GPU has MMU, it does not strictly need
boot time memory reservation and can work just fine with
just dynamic memory allocation. There have been no evidences
presented in favour of keeping this boot time memory
reservation. Also the Mali400 MP2 GPU on sun7i hardware
does not currently use this boot time memory reservation
at all.

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
sunxi: cedar: Fix oops on loading/unloading the cedar module

If we try to repeatedly load and unload the sunxi cedar module, we get
the following problem on the second round:

[   29.470000] [cedar dev]: install start!!!
[   29.470000] Unable to handle kernel paging request at virtual address bf0b138c
[   29.480000] pgd = df060000
[   29.480000] [bf0b138c] *pgd=5e69c811, *pte=00000000, *ppte=00000000
[   29.480000] Internal error: Oops: 7 [#1] PREEMPT ARM

Adding the missing del_timer() and platform_device_unregister() calls
to cedarv_exit() resolves this.

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
sunxi: cedar: Allow to use CMA for cedar memory allocation

In the case if the kernel supports CMA and has it enabled, now
the cedar module tries to allocate the 80MB memory buffer from CMA.
This memory block is kept in use as long as the cedar module is
loaded. When the module is unloaded, the allocated memory gets
released.

It is preferable to allocate cedar memory buffer from the first
256MB of physical memory to avoid bugs even though in theory
higher addresses might be supported:
    http://irclog.whitequark.org/linux-sunxi/2013-07-17#4409315;
In practice, both VLC (using the proprietary libve library) and
libvdpau-sunxi fail for the buffers allocated from above 256MB
(or partially crossing this boundary).

For the kernels without CMA, the old behaviour is preserved.

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>