RDMA: Split kernel-only global device caps from uverbs device caps

Split out flags from ib_device::device_cap_flags that are only used
internally to the kernel into kernel_cap_flags that is not part of the
uapi. This limits the device_cap_flags to being the same bitmap that will
be copied to userspace.

This cleanly splits out the uverbs flags from the kernel flags to avoid
confusion in the flags bitmap.

Add some short comments describing which each of the kernel flags is
connected to. Remove unused kernel flags.

Link: https://lore.kernel.org/r/0-v2-22c19e565eef+139a-kern_caps_jgg@nvidia.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

include/uapi/rdma/ib_user_verbs.h

@@ -1298,6 +1298,10 @@ struct ib_uverbs_ex_modify_cq {
 
 #define IB_DEVICE_NAME_MAX 64
 
+/*
+ * bits 9, 15, 16, 19, 22, 27, 30, 31, 32, 33, 35 and 37 may be set by old
+ * kernels and should not be used.
+ */
 enum ib_uverbs_device_cap_flags {
 	IB_UVERBS_DEVICE_RESIZE_MAX_WR = 1 << 0,
 	IB_UVERBS_DEVICE_BAD_PKEY_CNTR = 1 << 1,