Remove the obsolete mkfont.c and font_10x18.h

The font_10x18.h is used as a fall back for fonts if the
$(recovery_font) under bootable/recovery/fonts failed to reload. This
font looks very small on the screen and we haven't used it in a while.
Plus, fonts in header doesn't have many benefits if we support only
ascii characters. So we decide to remove this header along with the mkfont.c
that generates the header.

For reference, here's the steps to use mkfont:
1. Generate a picture of fonts with apps on host
2. Open the pic with GIMP
3. Export the pic as '.c' file, and rename it into '.h' file
4. Compile the generated '.h' file with mkfont.c

Bug: 76420958
Test: build and check the recovery menu on angler
Change-Id: I6c108aa43a07bf4994115ef764275bd84df725e1
diff --git a/minui/graphics.cpp b/minui/graphics.cpp
index 56f471b..202ce71 100644
--- a/minui/graphics.cpp
+++ b/minui/graphics.cpp
@@ -23,7 +23,6 @@
 
 #include <memory>
 
-#include "font_10x18.h"
 #include "graphics_adf.h"
 #include "graphics_drm.h"
 #include "graphics_fbdev.h"
@@ -313,42 +312,16 @@
   return 0;
 }
 
-static void gr_init_font(void) {
-  int res = gr_init_font("font", &gr_font);
-  if (res == 0) {
-    return;
-  }
-
-  printf("failed to read font: res=%d\n", res);
-
-  // fall back to the compiled-in font.
-  gr_font = static_cast<GRFont*>(calloc(1, sizeof(*gr_font)));
-  gr_font->texture = static_cast<GRSurface*>(malloc(sizeof(*gr_font->texture)));
-  gr_font->texture->width = font.width;
-  gr_font->texture->height = font.height;
-  gr_font->texture->row_bytes = font.width;
-  gr_font->texture->pixel_bytes = 1;
-
-  unsigned char* bits = static_cast<unsigned char*>(malloc(font.width * font.height));
-  gr_font->texture->data = bits;
-
-  unsigned char data;
-  unsigned char* in = font.rundata;
-  while ((data = *in++)) {
-    memset(bits, (data & 0x80) ? 255 : 0, data & 0x7f);
-    bits += (data & 0x7f);
-  }
-
-  gr_font->char_width = font.char_width;
-  gr_font->char_height = font.char_height;
-}
-
 void gr_flip() {
   gr_draw = gr_backend->Flip();
 }
 
 int gr_init() {
-  gr_init_font();
+  int ret = gr_init_font("font", &gr_font);
+  if (ret != 0) {
+    printf("Failed to init font: %d\n", ret);
+    return -1;
+  }
 
   auto backend = std::unique_ptr<MinuiBackend>{ std::make_unique<MinuiBackendAdf>() };
   gr_draw = backend->Init();