Add OPUS_ARM_INLINE_DOTPROD dotprod check

fixes:
  ../meson.build:322:9: ERROR: Unknown variable "opus_arm_may_have_dotprod"

after:
  dotprod check passes through.

Checking if "compiler supports gcc-style inline assembly" compiles: YES
Checking if "assembler supports EDSP instructions on ARM" compiles: YES
Checking if "assembler supports ARMv6 media instructions on ARM" compiles: YES
Checking if "assembler supports NEON instructions on ARM" compiles: YES
Checking if "assembler supports DOTPROD instructions on ARM" compiles: NO
Program perl found: YES (/usr/bin/perl)
Fetching value of define "__APPLE__" : (undefined)
Checking if "compiler supports ARMv7/AArch64 NEON intrinsics" : links: YES
Checking if "compiler supports AArch64 NEON intrinsics" : links: NO
Checking if "compiler supports AArch64 NEON intrinsics with -mfpu=neon" : links: NO
Message: Compiler does not support AArch64 NEON intrinsics
Checking if "compiler supports AArch64 DOTPROD intrinsics" : links: NO
Checking if "compiler supports AArch64 DOTPROD intrinsics with -march=armv8.2-a+dotprod" : links: NO
Message: Compiler does not support AArch64 DOTPROD intrinsics

refer:
- https://community.arm.com/arm-community-blogs/b/tools-software-ides-blog/posts/exploring-the-arm-dot-product-instructions



test with:
armv7ve-none-linux-gnueabihf-gcc test.c
/tmp/cc02sooK.s: Assembler messages:
/tmp/cc02sooK.s:32: Error: bad instruction `udot v0.4s,v1.16b,v2.16b'

aarch64-none-linux-gnu-gcc test.c
/tmp/ccnVi9Ec.s: Assembler messages:
/tmp/ccnVi9Ec.s:12: Error: selected processor does not support `udot v0.4s,v1.16b,v2.16b'

aarch64-none-linux-gnu-gcc -march=armv8.2-a+dotprod test.c

Signed-off-by: Rudi Heitbaum <rudi@heitbaum.com>
Signed-off-by: Jean-Marc Valin <jmvalin@jmvalin.ca>