OBJ_bsearch_ex_(): Fix const qualifier warning with CHARSET_EBCDIC

Fixes #31161

When building with CHARSET_EBCDIC defined,the compiler warns about
discarding the 'const' qualifier when assigning from base_[i * size]
to the non-const pointer p1:

`warning: assignment discards 'const' qualifier from pointer target type`

Change p1 from 'char *' to 'const char *' to maintain const-correctness
since the data being pointed to should not be modified through this
pointer.

Additionally, remove the unused variables l and h that were left over
from a previous implementation of the fallback linear search. These
variables served no purpose and only generated unused variable warnings.

Reviewed-by: Frederik Wedel-Heinen <fwh.openssl@gmail.com>
Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Tomas Mraz <tomas@openssl.foundation>
MergeDate: Mon May 18 11:07:53 2026
(Merged from https://github.com/openssl/openssl/pull/31173)

crypto/objects/obj_dat.c

diff --git a/crypto/objects/obj_dat.c b/crypto/objects/obj_dat.c
index 8bb029a..8ab0634 100644
--- a/crypto/objects/obj_dat.c
+++ b/crypto/objects/obj_dat.c
@@ -616,8 +616,8 @@
      */
     if (p == NULL) {
         const char *base_ = base;
-        int l, h, i = 0, c = 0;
-        char *p1;
+        int i = 0, c = 0;
+        const char *p1;
 
         for (i = 0; i < num; ++i) {
             p1 = &(base_[i * size]);