btm: allow BTM_VSC_CHIP_CAPABILITY_RSP_LEN_M_RELEASE to be adjustable

Some BCM firmwares shipped with LGE devices will not pass a check involving the BTM_VSC_CHIP_CAPABILITY_RSP_LEN_M_RELEASE capability.

This commit allows BTM_VSC_CHIP_CAPABILITY_RSP_LEN_M_RELEASE to be adjusted as a workaround for these firmwares.
This issue was seen on some v20 and g5 oreo release BCM firmwares and the BCM4358A3_001.004.015.0095.0168_KR_ORC.HCD fw found
on the v20 f800k pie release (lge/elsa_kt_kr/elsa:9/PKQ1.190522.001/20192161159c5)

Log snippet:
```
08-14 11:16:52.534  3468  3468 F DEBUG   : Abort message: '[FATAL:btm_ble_gap.cc(668)] Check failed: p_vcs_cplt_params->param_len >= BTM_VSC_CHIP_CAPABILITY_RSP_LEN_M_RELEASE.
```

Change-Id: I1fccfd0f8877bdc878e7a2068f654369b136956e
diff --git a/system/stack/btm/btm_ble_gap.cc b/system/stack/btm/btm_ble_gap.cc
index 1417440..d58ed8f 100644
--- a/system/stack/btm/btm_ble_gap.cc
+++ b/system/stack/btm/btm_ble_gap.cc
@@ -77,7 +77,11 @@
 #define BTM_VSC_CHIP_CAPABILITY_RSP_LEN 9
 #define BTM_VSC_CHIP_CAPABILITY_RSP_LEN_L_RELEASE \
   BTM_VSC_CHIP_CAPABILITY_RSP_LEN
+
+#ifndef BTM_VSC_CHIP_CAPABILITY_RSP_LEN_M_RELEASE
 #define BTM_VSC_CHIP_CAPABILITY_RSP_LEN_M_RELEASE 15
+#endif
+
 #define BTM_VSC_CHIP_CAPABILITY_RSP_LEN_S_RELEASE 25
 
 namespace {