block: Remove compiler built in function checks for bio_set_op_attrs

With the new optimization changes and new flag support makes SDLLVM 8.0
to behave different on few built in compiler functions than that of GCC.
This causing a compilation break with clang.

So, remove compiler built in function checks that don't have
any functional impact to fix this compilation errors.

Change-Id: I71ba68baeba7df905c6f05eeb39cbfa97f20e1bb
Signed-off-by: Naitik Bharadiya <bharad@codeaurora.org>