Fix C/107926: Wrong error message when initializing char array

The problem here is the code which handles {"a"} is supposed
to handle the case where the is something after the string but
it only handles the case where there is another string so
we go down the other path and error out saying "excess elements
in struct initializer" even though this was a character array.
To fix this, we need to move the ckeck if the initializer is
a string after the check for array and initializer.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

Thanks,
Adnrew Pinski

gcc/c/ChangeLog:

	PR c/107926
	* c-typeck.cc (process_init_element): Move the check
	for string cst until after the error message.

gcc/testsuite/ChangeLog:

	PR c/107926
	* gcc.dg/init-excess-3.c: New test.