target-mips: fix 64-bit FPU config for user-mode emulation

FR bit should be initialized to 1 for MIPS64, under condition that this
bit is writable and that CPU has an FPU unit. It should be initialized to
zero for MIPS32.
This fixes different MIPS32 issues with FPU instructions whose behaviour
defaulted to 64-bit FPU mode.

Signed-off-by: Petar Jovanovic <petar.jovanovic@imgtec.com>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
(cherry picked from commit 4d66261f71f2efa31e1052e4041c5ee505572fe5)

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>