[mlir] Fix a warning
This patch fixes:
mlir/lib/Dialect/SCF/Transforms/TileUsingInterface.cpp:1066:62:
error: missing field 'mergeOps' initializer
[-Werror,-Wmissing-field-initializers]
mlir/lib/Dialect/SCF/Transforms/TileUsingInterface.cpp:1076:75:
error: missing field 'mergeOps' initializer
[-Werror,-Wmissing-field-initializers]
