fastboot: Refactor bootimg_utils.cpp:mkbootimg()

Change mkbootimg() to return void, as we already have a |out| parameter.

Bug: 183455415
Test: Presubmit
Change-Id: I51439e273752ab9e21f8d7138e900ea55bdfdfc0
diff --git a/fastboot/bootimg_utils.cpp b/fastboot/bootimg_utils.cpp
index 6ba751a..d2056aa 100644
--- a/fastboot/bootimg_utils.cpp
+++ b/fastboot/bootimg_utils.cpp
@@ -47,9 +47,9 @@
     strcpy(reinterpret_cast<char*>(h->cmdline), cmdline.c_str());
 }
 
-static boot_img_hdr_v3* mkbootimg_v3_and_above(const std::vector<char>& kernel,
-                                               const std::vector<char>& ramdisk,
-                                               const boot_img_hdr_v2& src, std::vector<char>* out) {
+static void mkbootimg_v3_and_above(const std::vector<char>& kernel,
+                                   const std::vector<char>& ramdisk, const boot_img_hdr_v2& src,
+                                   std::vector<char>* out) {
 #define V3_PAGE_SIZE 4096
     const size_t page_mask = V3_PAGE_SIZE - 1;
     int64_t kernel_actual = (kernel.size() + page_mask) & (~page_mask);
@@ -74,20 +74,18 @@
 
     memcpy(hdr->magic + V3_PAGE_SIZE, kernel.data(), kernel.size());
     memcpy(hdr->magic + V3_PAGE_SIZE + kernel_actual, ramdisk.data(), ramdisk.size());
-
-    return hdr;
 }
 
-boot_img_hdr_v2* mkbootimg(const std::vector<char>& kernel, const std::vector<char>& ramdisk,
-                           const std::vector<char>& second, const std::vector<char>& dtb,
-                           size_t base, const boot_img_hdr_v2& src, std::vector<char>* out) {
+void mkbootimg(const std::vector<char>& kernel, const std::vector<char>& ramdisk,
+               const std::vector<char>& second, const std::vector<char>& dtb, size_t base,
+               const boot_img_hdr_v2& src, std::vector<char>* out) {
     if (src.header_version >= 3) {
         if (!second.empty() || !dtb.empty()) {
             die("Second stage bootloader and dtb not supported in v%d boot image\n",
                 src.header_version);
         }
-        return reinterpret_cast<boot_img_hdr_v2*>(
-                mkbootimg_v3_and_above(kernel, ramdisk, src, out));
+        mkbootimg_v3_and_above(kernel, ramdisk, src, out);
+        return;
     }
     const size_t page_mask = src.page_size - 1;
 
@@ -129,5 +127,4 @@
            second.size());
     memcpy(hdr->magic + hdr->page_size + kernel_actual + ramdisk_actual + second_actual, dtb.data(),
            dtb.size());
-    return hdr;
 }