hush: re-sequence includes

hush: re-sequence includes

'make tests' on a 32bit ARM system leads to

In file included from ../common/cli_hush.c:79:
../include/malloc.h:364:7: error: conflicting types for ‘memset’
 void* memset(void*, int, size_t);
       ^~~~~~
In file included from ../include/compiler.h:126,
                 from ../include/env.h:12,
                 from ../common/cli_hush.c:78:
../include/linux/string.h:103:15:
note: previous declaration of ‘memset’ was here
 extern void * memset(void *,int,__kernel_size_t);
               ^~~~~~
In file included from ../common/cli_hush.c:79:
../include/malloc.h:365:7: error: conflicting types for ‘memcpy’
 void* memcpy(void*, const void*, size_t);
       ^~~~~~
In file included from ../include/compiler.h:126,
                 from ../include/env.h:12,
                 from ../common/cli_hush.c:78:
../include/linux/string.h:106:15:
note: previous declaration of ‘memcpy’ was here
 extern void * memcpy(void *,const void *,__kernel_size_t);
        ^~~~~~

According to the U-Boot coding style guide common.h should be the first
include.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>