The only storage class specifier that is valid in a parameter declaration is register, we can see this from the draft C99 standard section 6.7.5.3
Function declarators (including prototypes) paragraph 2 which says:
The only storage-class specifier that shall occur in a parameter declaration is register.
this is section 6.7.6.3
in C11.
the storage class specifiers from section 6.7.1
Storage-class specifiers are as follows:
typedef
extern
static
auto
register