Without this flag, gcc generates code to save the Q/V registers to the
stack for handling the va_list in pr_print(). Saving the registers is
useless, as the registers are never restored, but accessing the
registers to save them hangs the CPU.

Follow the Linux arch/arm64/Makefile and use the general-regs-only flag
to prevent usage of floating point and Advanced SIMD register.

Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>