RTEMS | RISC-V: add support for using the MMU in S-Mode (!1182)

[Gedare Bloom (@gedare)]

Gedare Bloom created a merge request: https://gitlab.rtems.org/rtems/rtos/rtems/-/merge_requests/1182

Project:Branches: gedare/rtems:riscv-satp-init to rtems/rtos/rtems:main
Author:   Gedare Bloom



## Summary

Add basic support for MMU.

Closes #5540 

## Testing

I have to hunt down the `spconsole01.exe` failure. It's probably an issue with the mmio register r/w access sync'ing.

### Uniprocessor s-mode

config.ini:
```
[riscv/rv64imafdc_s]
INHERIT = rv64imafdc
RISCV_RAM_REGION_BEGIN = 0x84000000
RISCV_RAM_REGION_SIZE =  0x03000000
RISCV_USE_S_MODE = True
```

Tester
```
rtems-test --rtems-bsp=rv64imafdc_smode build/riscv/rv64imafdc_s/testsuites/sptests
...
Passed:        221
Failed:          1
User Input:      0
Expected Fail:   0
Indeterminate:   0
Benchmark:       0
Timeout:         1
Test too long:   0
Invalid:         0
Wrong Version:   0
Wrong Build:     0
Wrong Tools:     0
Wrong Header:    0
------------------
Total:         223
Failures:
 sp69.exe
Timeouts:
 spconsole01.exe
```

### SMP s-mode

```
[riscv/rv64imafdc_s_smp]
INHERIT = rv64imafdc_s
RTEMS_SMP = True
```

```
rtems-test --rtems-bsp=rv64imafdc_smode_smp build/riscv/rv64imafdc_s_smp/testsuites/smptests
...
Passed:        58
Failed:         2
User Input:     0
Expected Fail:  0
Indeterminate:  0
Benchmark:      0
Timeout:        0
Test too long:  0
Invalid:        0
Wrong Version:  0
Wrong Build:    0
Wrong Tools:    0
Wrong Header:   0
-----------------
Total:         60
Failures:
 smpmrsp01.exe
 smpschededf01.exe
```
These more or less match the results for SMP with M-Mode (it fails on smpfatal01.exe but not smpschededf01.exe).

## Generative AI

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