[MC][BPF] Add bpf guard for MC test data-section-prefix.ll

Commit f27c490 ("MC: Add .data. and .rodata. prefixes to MCContext
section classification") added a test assuming bpf target. But it
is possible bpf target is not configured in the clang build.
Let us add explicit bpf-target requirement for the test
so the test can be ingored properly for clang build without enabling
bpf target.

llvm/test/MC/ELF/data-section-prefix.ll

@@ -1,3 +1,5 @@
+; REQUIRES: bpf-registered-target
+
 ; RUN: llc -filetype obj -o - %s | llvm-readobj --sections - | FileCheck --check-prefix="SECTIONS" %s
 ;
 ; SECTIONS:         Name: .data.A