README.md: Fix MD010 warnings

The following warnings are generated by using markdownlint analysis:
```
README.md:150:1 MD010/no-hard-tabs Hard tabs [Column: 1]
README.md:151:1 MD010/no-hard-tabs Hard tabs [Column: 1]
README.md:152:1 MD010/no-hard-tabs Hard tabs [Column: 1]
```
Refer to markdown-lint [1] to fix MD010
[1]: https://github.com/updownpress/markdown-lint/blob/master/rules/010-no-hard-tabs.md

Signed-off-by: George Liu <liuxiwei@ieisystem.com>
Change-Id: I7066e286d1b8849f311fef0472f8766ada0dd05e
diff --git a/README.md b/README.md
index 5aae834..874ad22 100644
--- a/README.md
+++ b/README.md
@@ -147,9 +147,9 @@
 ```c
 LIBPLDM_ABI_TESTING
 pldm_requester_rc_t pldm_transport_send_msg(struct pldm_transport *transport,
-					    pldm_tid_t tid,
-					    const void *pldm_req_msg,
-					    size_t req_msg_len)
+                                            pldm_tid_t tid,
+                                            const void *pldm_req_msg,
+                                            size_t req_msg_len)
 {
     ...
 }