nfs/blocklayout: Fix compilation error (`make W=1`) in bl_write_pagelist()

nfs/blocklayout: Fix compilation error (`make W=1`) in bl_write_pagelist()

Clang compiler is not happy about set but unused variable
(when dprintk() is no-op):

.../blocklayout/blocklayout.c:384:9: error: variable 'count' set but not used [-Werror,-Wunused-but-set-variable]

Remove a leftover from the previous cleanup.

Fixes: 3a6fd1f004fc ("pnfs/blocklayout: remove read-modify-write handling in bl_write_pagelist")
Acked-by: Anna Schumaker <anna.schumkaer@oracle.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>