selftests/zram: replace ZRAM_LZ4_COMPRESS

Since commit ce1ed9f9
("zram: delete custom lzo/lz4")

we need CONFIG_CRYPTO_LZ4=y instead of
CONFIG_ZRAM_LZ4_COMPRESS
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>

tools/testing/selftests/zram/README

@@ -13,7 +13,7 @@ Statistics for individual zram devices are exported through sysfs nodes at
 
 Kconfig required:
 CONFIG_ZRAM=y
-CONFIG_ZRAM_LZ4_COMPRESS=y
+CONFIG_CRYPTO_LZ4=y
 CONFIG_ZPOOL=y
 CONFIG_ZSMALLOC=y