clang-tidy: Replace NULL with nullptr

Replaced all instances of NULL with nullptr to improve type safety
and clarity, as nullptr is the modern C++ standard for null pointers.

Tested: Build verified

Change-Id: I0e0749db217667d9c3f51f8fac6cb58e8915e8d2
Signed-off-by: Jayanth Othayoth <ojayanth@gmail.com>
diff --git a/frup.cpp b/frup.cpp
index fb06e80..7254017 100644
--- a/frup.cpp
+++ b/frup.cpp
@@ -296,7 +296,7 @@
     while (area_offset < areabuflen &&
            areabufptr[area_offset] != IPMI_FRU_SENTINEL_VALUE)
     {
-        ipmi_fru_field_t* field_ptr = NULL;
+        ipmi_fru_field_t* field_ptr = nullptr;
 
         if (chassis_custom_fields && chassis_custom_fields_len)
         {
@@ -424,7 +424,7 @@
     while (area_offset < areabuflen &&
            areabufptr[area_offset] != IPMI_FRU_SENTINEL_VALUE)
     {
-        ipmi_fru_field_t* field_ptr = NULL;
+        ipmi_fru_field_t* field_ptr = nullptr;
 
         if (board_custom_fields && board_custom_fields_len)
         {
@@ -562,7 +562,7 @@
     while (area_offset < areabuflen &&
            areabufptr[area_offset] != IPMI_FRU_SENTINEL_VALUE)
     {
-        ipmi_fru_field_t* field_ptr = NULL;
+        ipmi_fru_field_t* field_ptr = nullptr;
 
         if (product_custom_fields && product_custom_fields_len)
         {
@@ -666,7 +666,7 @@
     if (bin_in_ascii)
     {
         free(bin_in_ascii);
-        bin_in_ascii = NULL;
+        bin_in_ascii = nullptr;
     }
 }
 
@@ -734,7 +734,7 @@
             printf("Board : Buf len = [%d]\n", len);
 #endif
             ipmi_fru_board_info_area(
-                (uint8_t*)msgbuf + 2, len, NULL, &mfg_date_time,
+                (uint8_t*)msgbuf + 2, len, nullptr, &mfg_date_time,
                 &vpd_info[OPENBMC_VPD_KEY_BOARD_MFR],
                 &vpd_info[OPENBMC_VPD_KEY_BOARD_NAME],
                 &vpd_info[OPENBMC_VPD_KEY_BOARD_SERIAL_NUM],
@@ -766,7 +766,7 @@
             printf("Product : Buf len = [%d]\n", len);
 #endif
             ipmi_fru_product_info_area(
-                (uint8_t*)msgbuf + 2, len, NULL,
+                (uint8_t*)msgbuf + 2, len, nullptr,
                 &vpd_info[OPENBMC_VPD_KEY_PRODUCT_MFR],
                 &vpd_info[OPENBMC_VPD_KEY_PRODUCT_NAME],
                 &vpd_info[OPENBMC_VPD_KEY_PRODUCT_PART_MODEL_NUM],