Relocation and analysis improvement for Renesas RX

[Heersin]

Your checklist for this pull request

• I've read the guidelines for contributing to this repository
• I made sure to follow the project's coding style
• I've documented or updated the documentation of every function and struct this PR changes. If not so I've explained why.
• I've added tests that prove my fix is effective or that my feature works (if possible)
• I've updated the rizin book with the relevant information (if needed)

Detailed description

• stack pointer
• relocation for rx-elf obj
• mnemonic sdb

Test plan

Test with an rx-elf object which compiled from the following source:

static int local_static_gint;
int local_gint;
extern unsigned short extern_int;

void extern_foo();
void bottom_foo();

static void static_foo() {
    return;
}

void top_foo() {
    static int static_bar = 0x01;

    static_bar = 0x02;
    return;
}

int main() {
    int local_i = 1;

    local_gint = 0x1234;
    int x = -local_gint;
    extern_int = 0x67;
    local_static_gint = 0xabcd;

    static_foo();
    extern_foo();
    top_foo();

    // void (*fn_ptr)() = &extern_foo;
    // fn_ptr();

    bottom_foo();

    return 0;
}

void bottom_foo() {
    int x = 10;
    return;
}

compile command: rx-elf-gcc -c reloc_tmp.c -o reloc_tmp.o ; and check with rx-elf-readelf and rx-elf-ld

Closing issues

...