graphics/opencv: add local patch

- the patch on github has changed a few times (by dropping two
  characters).
- instead of having it fail to fetch regularly, just add the patch to
  files/

Reported by:	yuri

graphics/opencv/Makefile

@@ -3,9 +3,6 @@ DISTVERSION=	4.5.3
 PORTREVISION=	5
 CATEGORIES=	graphics
 
-PATCH_SITES=	https://github.com/opencv/opencv/commit/
-PATCHFILES=	998406d20e93aa36b26fd56506f3ea8a82b43c24.patch:-p1
-
 MAINTAINER=	tcberner@FreeBSD.org
 COMMENT=	Open Source Computer Vision library
 

graphics/opencv/distinfo

@@ -15,5 +15,3 @@ SHA256 (opencv-opencv_3rdparty-8afa57abc8229d611c4937165d20e2a2d9fc5a12_GH0.tar.
 SIZE (opencv-opencv_3rdparty-8afa57abc8229d611c4937165d20e2a2d9fc5a12_GH0.tar.gz) = 63301261
 SHA256 (opencv-opencv_3rdparty-a56b6ac6f030c312b2dce17430eef13aed9af274_GH0.tar.gz) = 6d3552455d927dd28cdd6a78470398208ff2167b19b0dd51ab30a241d900cb4c
 SIZE (opencv-opencv_3rdparty-a56b6ac6f030c312b2dce17430eef13aed9af274_GH0.tar.gz) = 135706483
-SHA256 (998406d20e93aa36b26fd56506f3ea8a82b43c24.patch) = bce0f541613ac800c9f84bffde2f21b035b0528035e89495e7a49c94546334b7
-SIZE (998406d20e93aa36b26fd56506f3ea8a82b43c24.patch) = 1074

graphics/opencv/files/patch-git_998406d

@@ -0,0 +1,31 @@
+From f7b4b750d8930b5bb6696cea6d609dc70a0597db Mon Sep 17 00:00:00 2001
+From: mikael <mikael@FreeBSD.org>
+Date: Tue, 21 Sep 2021 19:46:33 +0200
+Subject: [PATCH] Detect FP16 on FreeBSD aarch64
+
+---
+ modules/core/src/system.cpp | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git modules/core/src/system.cpp modules/core/src/system.cpp
+index d8b8f6755950..df9e8a0ce76f 100644
+--- modules/core/src/system.cpp
++++ modules/core/src/system.cpp
+@@ -533,7 +533,7 @@ struct HWFeatures
+         }
+     #endif // CV_CPUID_X86
+
+-    #if defined __ANDROID__ || defined __linux__
++    #if defined __ANDROID__ || defined __linux__ || defined __FreeBSD__
+     #ifdef __aarch64__
+         have[CV_CPU_NEON] = true;
+         have[CV_CPU_FP16] = true;
+@@ -559,7 +559,7 @@ struct HWFeatures
+         CV_LOG_INFO(NULL, "- FP16 instructions is NOT enabled via build flags");
+         #endif
+       #endif
+-    #elif defined __arm__
++    #elif defined __arm__ && !defined __FreeBSD__
+         int cpufile = open("/proc/self/auxv", O_RDONLY);
+
+         if (cpufile >= 0)