zdump: dfi_elf: refactor nt_* functions

The functions are refactored so the `struct zg_fh` value is now passed as
argument to the `nt_*` functions instead of accessing the global variable `g.fh`
from within of the functions. This makes the functions reusable and easier to
test. While at it, improve the documentation of `nt_read`.

Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

zdump/df_elf.h

@@ -156,6 +156,16 @@ int read_elf_hdr(const struct zg_fh *fh, Elf64_Ehdr *ehdr);
 Elf64_Phdr *read_elf_phdrs(const struct zg_fh *fh, const Elf64_Ehdr *ehdr,
 			   unsigned int *phdr_count);
 
+/*
+ * Read note and store the note description in @buf
+ */
+int nt_read(const struct zg_fh *fh, const Elf64_Nhdr *note, void *buf, size_t buf_len);
+
+/*
+ * Skip note
+ */
+void nt_skip(const struct zg_fh *fh, const Elf64_Nhdr *note);
+
 /*
  * Initialize ELF note
  */