test/compress: fix build

test/compress: fix build

Fixed the compilation error:

app/test/test_compressdev.c:1949:11: note:
	previous definition of 'i' was here
app/test/test_compressdev.c:1992:2: error:
	'for' loop initial declarations are only allowed in C99 mode
app/test/test_compressdev.c:1992:2: note:
	use option -std=c99 or -std=gnu99 to compile your code
app/test/test_compressdev.c:1996:19: warning:
	assignment from incompatible pointer type [enabled by default]

Fixes: 355b02eedc65 ("test/compress: add max mbuf size test case")

Signed-off-by: Tomasz Jozwiak <tomaszx.jozwiak@intel.com>
Signed-off-by: Fiona Trahe <fiona.trahe@intel.com>