zlib: export S390 symbols for zlib modules

Fix build errors when ZLIB_INFLATE=m and ZLIB_DEFLATE=m and ZLIB_DFLTCC=y
by exporting the 2 needed symbols in dfltcc_inflate.c.

Fixes these build errors:

  ERROR: modpost: "dfltcc_inflate" [lib/zlib_inflate/zlib_inflate.ko] undefined!
  ERROR: modpost: "dfltcc_can_inflate" [lib/zlib_inflate/zlib_inflate.ko] undefined!

Fixes: 1261961 ("lib/zlib: add s390 hardware support for kernel zlib_inflate")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Link: https://lkml.kernel.org/r/20201123191712.4882-1-rdunlap@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/zlib_dfltcc/dfltcc_inflate.c

@@ -4,6 +4,7 @@
 #include "dfltcc_util.h"
 #include "dfltcc.h"
 #include <asm/setup.h>
+#include <linux/export.h>
 #include <linux/zutil.h>
 
 /*
@@ -29,6 +30,7 @@ int dfltcc_can_inflate(
     return is_bit_set(dfltcc_state->af.fns, DFLTCC_XPND) &&
                is_bit_set(dfltcc_state->af.fmts, DFLTCC_FMT0);
 }
+EXPORT_SYMBOL(dfltcc_can_inflate);
 
 static int dfltcc_was_inflate_used(
     z_streamp strm
@@ -147,3 +149,4 @@ dfltcc_inflate_action dfltcc_inflate(
     return (cc == DFLTCC_CC_OP1_TOO_SHORT || cc == DFLTCC_CC_OP2_TOO_SHORT) ?
         DFLTCC_INFLATE_BREAK : DFLTCC_INFLATE_CONTINUE;
 }
+EXPORT_SYMBOL(dfltcc_inflate);