Patch merged into coreboot/master: commonlib/lz4_wrapper: Use correct casts to ensure valid calculations

the following patch was just integrated into master:
commit 87fe2360c4b8b1f3f475e1669e48c7c2ae7b242a
Author: Paul Menzel 
Date:   Tue Feb 23 18:59:04 2016 +0100

commonlib/lz4_wrapper: Use correct casts to ensure valid calculations

Commit 09f2921b (cbfs: Add LZ4 in-place decompression support for
    pre-RAM stages) breaks building cbfstool with gcc (Debian 4.9.2-10)
    4.9.2 in Debian 8.3 (jessie) with a 32-bit user space. It works fine
    in a 64-bit user space.

```
    /home/joey/src/coreboot/src/commonlib/lz4_wrapper.c:164:18: note: in expansion of macro 'MIN'
        size_t size = MIN((uint32_t)b.size, dst + dstn - out);
                      ^
    /home/joey/src/coreboot/src/commonlib/include/commonlib/helpers.h:29:35: error: signed and unsigned type in conditional expression [-Werror=sign-compare]
     #define MIN(a,b) ((a) < (b) ? (a) : (b))
                                       ^
    ```

The problem is arithmetic on void*, so explicitly cast to the wanted
    types as suggested by user *redi* in #[e-mail].

Change-Id: I85bee25a69c432ef8bb934add7fd2e2e31f03662
    Signed-off-by: Paul Menzel 
    Reviewed-on: https://review.coreboot.org/13771
    Reviewed-by: Aaron Durbin 
    Tested-by: build bot (Jenkins)

See https://review.coreboot.org/13771 for details.

-gerrit