c: Update TLS model after processing a TLS variable

c: Update TLS model after processing a TLS variable

Set a tentative TLS model in grokvardecl and update TLS mode with the
default TLS access model after a TLS variable has been fully processed
if the default TLS access model is stronger.

gcc/c/

	PR c/107419
	* c-decl.cc (c_decl_attributes): Update TLS model with the
	default TLS access model if the default TLS access model is
	stronger.
	(grokdeclarator): Set a tentative TLS model which will be
	updated by c_decl_attributes later.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>