Only the e500v1/v2 cores have HID1[RXFE] so we should attempt to set or
clear this register bit on them.  Otherwise we get crashes like:

NIP: c0579f84 LR: c006d550 CTR: c0579f84
REGS: ef857ec0 TRAP: 0700   Not tainted  (2.6.38.2-00072-gf15ba3c)
MSR: 00021002 <ME,CE>  CR: 22044022  XER: 00000000
TASK = ef8559c0[1] 'swapper' THREAD: ef856000 CPU: 0
GPR00: c006d538 ef857f70 ef8559c0 00000000 00000004 00000000 00000000 00000000
GPR08: c0590000 c30170a8 00000000 c30170a8 00000001 0fffe000 00000000 00000000
GPR16: 00000000 7ffa0e60 00000000 00000000 7ffb0bd8 7ff3b844 c05be000 00000000
GPR24: 00000000 00000000 c05c28b0 c0579fac 00000000 00029002 00000000 c0579f84
NIP [c0579f84] mpc85xx_mc_clear_rfxe+0x0/0x28
LR [c006d550] on_each_cpu+0x34/0x50
Call Trace:
[ef857f70] [c006d538] on_each_cpu+0x1c/0x50 (unreliable)
[ef857f90] [c057a070] mpc85xx_mc_init+0xc4/0xdc
[ef857fa0] [c0001cd4] do_one_initcall+0x34/0x1a8
[ef857fd0] [c055d9d8] kernel_init+0x17c/0x218
[ef857ff0] [c000cda4] kernel_thread+0x4c/0x68
Instruction dump:
40be0018 3c60c052 3863c70c 4be9baad 3be0ffed 4bd7c99d 80010014 7fe3fb78
83e1000c 38210010 7c0803a6 4e800020 <7c11faa6> 54290024 81290008
3d60c06e
Oops: Exception in kernel mode, sig: 4 [#2]
---[ end trace 49ff3b8f93efde1a ]---

Also use the HID1_RFXE define rather than a magic number.
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>