Creating a Cortex M Linux Qiling instance causes `AttributeError`.

Describe the bug
Creating a Cortex M Qiling instance with a Linux ostype causes an AttributeError.

Sample Code

import qiling
qiling.Qiling(code=b"\0", archtype=qiling.const.QL_ARCH.CORTEX_M, ostype='linux')

Expected behavior
No error.

Result

Traceback (most recent call last):
  File "test.py", line 2, in <module>
    qiling.Qiling(code=b"\0", archtype=qiling.const.QL_ARCH.CORTEX_M, ostype='linux')
  File "~/.local/lib/python3.8/site-packages/qiling/core.py", line 179, in __init__
    self._os = select_os(ostype)(self)
  File "~/.local/lib/python3.8/site-packages/qiling/os/linux/linux.py", line 48, in __init__
    self.load()
  File "~/.local/lib/python3.8/site-packages/qiling/os/linux/linux.py", line 56, in load
    self.ql.arch.enable_vfp()
  File "~/.local/lib/python3.8/site-packages/qiling/arch/arm.py", line 104, in enable_vfp
    self.regs.c1_c0_2 = self.regs.c1_c0_2 | (0b11 << 20) | (0b11 << 22)
  File "~/.local/lib/python3.8/site-packages/qiling/arch/register.py", line 41, in __getattr__
    return super().__getattribute__(name)
AttributeError: 'QlRegisterManager' object has no attribute 'c1_c0_2'

Reproduce the sample with Cortex M and Linux, then inspect qiling/os/linux/linux.py where load() calls enable_vfp. Follow that call into qiling/arch/arm.py and qiling/arch/register.py to understand the missing register access. Done means the sample no longer raises AttributeError and the behavior is covered by a regression test.