t/nvmept_trim: increase transfer size for some tests

The final sequence of tests uses a block size of 4096 bytes. This can be
slow enough on some platforms to trigger a 10-minute timeout. Increase
the block size to 256K to reduce the run time.

Signed-off-by: Vincent Fu <vincent.fu@samsung.com>
diff --git a/t/nvmept_trim.py b/t/nvmept_trim.py
index 5756838..c990747 100755
--- a/t/nvmept_trim.py
+++ b/t/nvmept_trim.py
@@ -470,6 +470,7 @@
             "output-format": 'json',
             "buffer_pattern": 0x0f,
             "size": 256*1024*1024,
+            "bs": 256*1024,
             },
         "test_class": TrimTest,
     },
@@ -481,6 +482,7 @@
             "verify_pattern": 0x0f,
             "verify": "pattern",
             "size": 256*1024*1024,
+            "bs": 256*1024,
             },
         "test_class": TrimTest,
     },
@@ -491,6 +493,7 @@
             "num_range": 8,
             "output-format": 'json',
             "size": 128*1024*1024,
+            "bs": 256*1024,
             },
         "test_class": TrimTest,
     },
@@ -511,6 +514,7 @@
             "verify_pattern": 0x0f,
             "verify": "pattern",
             "size": 128*1024*1024,
+            "bs": 256*1024,
             },
         "test_class": TrimTest,
         "success": SUCCESS_NONZERO,
@@ -524,6 +528,7 @@
             "verify": "pattern",
             "offset": 128*1024*1024,
             "size": 128*1024*1024,
+            "bs": 256*1024,
             },
         "test_class": TrimTest,
     },