mtd: cfi_cmdset_0001: Support the absence of protection registers

[ Upstream commit b359ed51 ]

The flash controller implemented by the Arm Base platform behaves like
the Intel StrataFlash J3 device, but omits several features. In
particular it doesn't implement a protection register, so "Number of
Protection register fields" in the Primary Vendor-Specific Extended
Query, is 0.

The Intel StrataFlash J3 datasheet only lists 1 as a valid value for
NumProtectionFields. It describes the field as:

	"Number of Protection register fields in JEDEC ID space.
	“00h,” indicates that 256 protection bytes are available"

While a value of 0 may arguably not be architecturally valid, the
driver's current behavior is certainly wrong: if NumProtectionFields is
0, read_pri_intelext() adds a negative value to the unsigned extra_size,
and ends up in an infinite loop.

Fix it by ignoring a NumProtectionFields of 0.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Tested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Stable-dep-of: 565fe150 ("mtd: cfi_cmdset_0001: Byte swap OTP info")
Signed-off-by: Sasha Levin <sashal@kernel.org>