selftests/bpf: Fix bpf selftest build error

JIRA: https://issues.redhat.com/browse/RHEL-116876

commit 4b65d5a
Author: Saket Kumar Bhaskar <skb99@linux.ibm.com>
Date:   Mon May 12 14:41:07 2025 +0530

    selftests/bpf: Fix bpf selftest build error

    On linux-next, build for bpf selftest displays an error due to
    mismatch in the expected function signature of bpf_testmod_test_read
    and bpf_testmod_test_write.

    Commit 97d0680 ("sysfs: constify bin_attribute argument of bin_attribute::read/write()")
    changed the required type for struct bin_attribute to const struct bin_attribute.

    To resolve the error, update corresponding signature for the callback.

    Fixes: 97d0680 ("sysfs: constify bin_attribute argument of bin_attribute::read/write()")
    Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
    Closes: https://lore.kernel.org/all/e915da49-2b9a-4c4c-a34f-877f378129f6@linux.ibm.com/
    Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
    Signed-off-by: Saket Kumar Bhaskar <skb99@linux.ibm.com>
    Link: https://lore.kernel.org/r/20250512091108.2015615-1-skb99@linux.ibm.com
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Signed-off-by: Anusha Srivatsa <asrivats@redhat.com>

Author: anushasrivats

tools/testing/selftests/bpf/test_kmods/bpf_testmod.c

@@ -385,7 +385,7 @@ int bpf_testmod_fentry_ok;
 
 noinline ssize_t
 bpf_testmod_test_read(struct file *file, struct kobject *kobj,
-		      struct bin_attribute *bin_attr,
+		      const struct bin_attribute *bin_attr,
 		      char *buf, loff_t off, size_t len)
 {
 	struct bpf_testmod_test_read_ctx ctx = {
@@ -465,7 +465,7 @@ ALLOW_ERROR_INJECTION(bpf_testmod_test_read, ERRNO);
 
 noinline ssize_t
 bpf_testmod_test_write(struct file *file, struct kobject *kobj,
-		      struct bin_attribute *bin_attr,
+		      const struct bin_attribute *bin_attr,
 		      char *buf, loff_t off, size_t len)
 {
 	struct bpf_testmod_test_write_ctx ctx = {
@@ -567,7 +567,7 @@ static void testmod_unregister_uprobe(void)
 
 static ssize_t
 bpf_testmod_uprobe_write(struct file *file, struct kobject *kobj,
-			 struct bin_attribute *bin_attr,
+			 const struct bin_attribute *bin_attr,
 			 char *buf, loff_t off, size_t len)
 {
 	unsigned long offset = 0;