Do not trap access to floating point registers

Do not trap access to floating point registers

Traps when accessing architectural features are disabled by clearing bits
in CPTR_EL3 during early boot, including accesses to floating point
registers. The value of this register was previously undetermined, causing
unwanted traps to EL3. Future EL3 code (for example, context save/restore
code) may use floating point registers, although they are not used by current
code.

Also, the '-mgeneral-regs-only' flag is enabled in the GCC settings to
prevent generation of code that uses floating point registers.

Change-Id: I9a03675f6387bbbee81a6f2c9ccf81150db03747