Mesen labels for PCE's target fixed bank symbols are incorrect.

[est77]

Using the latest release (21.0.1), mesen labels for PCE fixed bank (bank0) symbols are offset by 0x2000 bytes.

Simple repro:

#include <pce.h>

[[noreturn]]
int main()
{
    while(true)
    {
    }
}

mos-pce-clang++ main.cpp -o test.pce

Result:

PcePrgRom:2000:_init PcePrgRom:2000:_start PcePrgRom:2019:_fini PcePrgRom:201a:nmi PcePrgRom:201b-201c:main PcePrgRom:201d-2021:exit PcePrgRom:2022-2037:__pce_psg_init PcePrgRom:2038-2070:__pce_vdc_init PcePrgRom:2071:irq_timer PcePrgRom:207b:irq_vdc PcePrgRom:2085:irq_ext PcePrgRom:3fd3:_early_start