mips: fix implicit export.h usage cases in cavium platform

mips: fix implicit export.h usage cases in cavium platform

Fixes the following failures:

arch/mips/cavium-octeon/csrc-octeon.c:138: error: type defaults to 'int' in declaration of 'EXPORT_SYMBOL'
arch/mips/cavium-octeon/dma-octeon.c:218: error: type defaults to 'int' in declaration of 'EXPORT_SYMBOL'
arch/mips/cavium-octeon/flash_setup.c:62: error: 'THIS_MODULE' undeclared (first use in this function)

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>