clang: Add Xtensa architecture support

Add support for the Xtensa CPU architecture to clang and lld. This is based on patches submitted upstream by Espressif.

The first commit adds patches that are identical to what's in Espressif's repository. The second commit fixes the LLD patch (made for LLVM 14.0.0) to work with 14.0.2. It removes a line setting noneRel to R_XTENSA_NONE; this is valid because noneRel is now constexpr 0 in the base class, and R_XTENSA_NONE is 0.

Signed-off-by: Bernhard Rosenkränzer bernhard.rosenkraenzer.ext@huawei.com